[PHYSICS]: Recoil before bullet leaves barrel?
Bret Jensen
# Put a 9-pound rifle with a 3-pound trigger burning twice or three times
# the powder behind three to four times the bullet weight in the hands of
# someone who isn't exactly holding the rifle the same for each shot and
# it's a different story. When free recoil energy goes from 3 pounds to 30
# pounds, there's going to be a lot more rifle movement before the bullet
# exits the muzzle.
COME ON. We all learned in high school physics that objects
maintain their momentum unless acted upon. Until the bullet leaves the
barrel there is no action to produce the "equal and opposite" reaction of
recoil.
I saw a series of high-speed strobe photos taken by Winchester in
the 50s in which they had the muzzle of a Model 94 resting on a black
block and a white sheet behind the rifle. With the bullet 1/2" out of
the muzzle, there was no white space yet visible between the muzzle and
block. With the bullet about 1 1/2 inch out of the muzzle, there was a
thin white line visible between muzzle and block. The pictures were
captioned, "Why felt recoil does not influence bullet strike," or
something close to that.
- Bret Jensen
Jim Nasset
Bret Jensen <bje...@willamette.edu> wrote in article
<5f5mal$l...@xring.cs.umd.edu>...
#
# # Put a 9-pound rifle with a 3-pound trigger burning twice or three times
# # the powder behind three to four times the bullet weight in the hands of
# # someone who isn't exactly holding the rifle the same for each shot and
# # it's a different story. When free recoil energy goes from 3 pounds to
30
# # pounds, there's going to be a lot more rifle movement before the bullet
# # exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
# maintain their momentum unless acted upon. Until the bullet leaves the
# barrel there is no action to produce the "equal and opposite" reaction of
# recoil.
Boy, you have opened a can of worms now. About a year ago I attempted to
explain to a number of "disbelievers" in the group that any (rearward)
rifle movement from recoil prior to the exit of the bullet from the muzzle
was insignificant. This is simply because the mass of the bullet and powder
moving down the barrel is insufficient to overcome the many times greater
at rest mass of the rifle. Because of the riflings however, there is a
small rotational force attempting to twist the rifle in the opposite
direction of the twist direction. This twist however would be essentially
the same for each bullet (traveling at substantially the same speed and
with the same bearing surface) therefore once the sights had been initially
adjusted, this cant is made up for. But get ready for a bunch of "opinions"
to the contrary.
Jim Nasset
Aftermarket Innovations
Michael Courtney
Bret Jensen (bje...@willamette.edu) wrote:
: # Put a 9-pound rifle with a 3-pound trigger burning twice or three times
: # the powder behind three to four times the bullet weight in the hands of
: # someone who isn't exactly holding the rifle the same for each shot and
: # it's a different story. When free recoil energy goes from 3 pounds to 30
: # pounds, there's going to be a lot more rifle movement before the bullet
: # exits the muzzle.
: COME ON. We all learned in high school physics that objects
: maintain their momentum unless acted upon. Until the bullet leaves the
: barrel there is no action to produce the "equal and opposite" reaction of
: recoil.
Not so. The gun begins moving backwards as soon as the bullet begins
moving forward in the barrel. If the gun/bullet were at rest to begin
with, total momentum is always zero until external forces on the gun
(your shoulder) bring it back to rest. If a bullet has gained 1600 fps
half-way down the barrel, the gun will already have rearward momentum
which compensates the bullet's momentum. My Ph.D. is in physics.
: I saw a series of high-speed strobe photos taken by Winchester in
: the 50s in which they had the muzzle of a Model 94 resting on a black
: block and a white sheet behind the rifle. With the bullet 1/2" out of
: the muzzle, there was no white space yet visible between the muzzle and
: block. With the bullet about 1 1/2 inch out of the muzzle, there was a
: thin white line visible between muzzle and block. The pictures were
: captioned, "Why felt recoil does not influence bullet strike," or
: something close to that.
This is more a matter of time than momentum. It only takes 0.001 seconds
for a bullet to leave the barrel. Even though the gun begins moving rearward
as soon as the bullet begins moving forward, it has not gone very far in the
millisecond or so it takes for the bullet to be out of the barrel. For a
7.5 lb 30-06 shooting a 150 grain bullet, the rearward motion is roughly
0.07". With a much bigger gun, the momentum of the exhaust gasses play a
much larger role, and combine with a larger bullet to produce a larger effect.
I would estimate that in the time it takes a bullet to leave the barrel,
a big game gun would move rearward roughly 0.21"
The effect on recoil on accuracy depends not on the rearward motion but on
the change in direction of the barrel as the bullet leaves. Conservation
of angular motion must be used here because it is rotational motion that
moves the barrel out of line. To compute this effect accurately requires
knowing the moment of inertia of the gun about its pivoting axis. These
parameters will vary widely depending on the gun and shooter. However, for
a rough estimate, I will assume that the barrel jumps up 5% of the amount
the rifle moves backward, or 0.007" for a 30-06 and 0.021" for a big game gun.
This effect produces a 0.5 MOA deflection in a 30-06 and a 1.5 MOA deflection
in the big game gun.
A person's strength is not nearly as important in reducing this effect as
the way they were holding the gun when they pulled the trigger, because
it's the way the gun is held and it's moment of inertia that determine
its pivoting axis. Usually, the pivoting axis is below the line of the
barrel bore, which is why the barrel moves up. If the pivoting axis
is on the bore line, then the angular momentum of the gun remains zero
and the gun doesn't move.
--
Michael Courtney, Ph. D.
mic...@amo.mit.edu
Rich Zuchowski
In <5f5mal$l...@xring.cs.umd.edu> Bret Jensen <bje...@willamette.edu> writes:
#
#
## Put a 9-pound rifle with a 3-pound trigger burning twice or three times
## the powder behind three to four times the bullet weight in the hands of
## someone who isn't exactly holding the rifle the same for each shot and
## it's a different story. When free recoil energy goes from 3 pounds to 30
## pounds, there's going to be a lot more rifle movement before the bullet
## exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
#maintain their momentum unless acted upon. Until the bullet leaves
the
#barrel there is no action to produce the "equal and opposite" reaction
of
#recoil.
# I saw a series of high-speed strobe photos taken by Winchester in
#the 50s in which they had the muzzle of a Model 94 resting on a black
#block and a white sheet behind the rifle. With the bullet 1/2" out of
#the muzzle, there was no white space yet visible between the muzzle
and
#block. With the bullet about 1 1/2 inch out of the muzzle, there was
a
#thin white line visible between muzzle and block. The pictures were
#captioned, "Why felt recoil does not influence bullet strike," or
#something close to that.
#
#
# - Bret Jensen
Well, if this is true, why is it that in the same gun, a lighter bullet
will impact the target LOWER than a heavier bullet?
r...@neosoft.com
Does the amount of "shoulder" you put behind the gun affect it's point
of impact? There must be a diference between putting the stock against a wall
vs. no resistance or only the weight of the gun itself I should say.
Imagining a spring between a ball and a variable surface helps to
visualize the effect. If one end is against a rigid surface the force will
mostly affect the ball, but if the spring is between two similar balls the
acceleration and velocity of each would be roughly halved.
Now whether this analogy transfers to firearms, and to what degree is
my question.
In article <5f5mal$l...@xring.cs.umd.edu>, Bret Jensen <bje...@willamette.edu>
wrote:
> ...
-Faber,S.R.
## Put a 9-pound rifle with a 3-pound trigger burning twice or three times
## the powder behind three to four times the bullet weight in the hands of
## someone who isn't exactly holding the rifle the same for each shot and
## it's a different story. When free recoil energy goes from 3 pounds to 30
## pounds, there's going to be a lot more rifle movement before the bullet
## exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
#maintain their momentum unless acted upon. Until the bullet leaves the
#barrel there is no action to produce the "equal and opposite" reaction of
#recoil.
You would expect the center of mass to stay at the same place as long
as the bullet is in the barrel. The center of mass at the start
is a little different than when the bullet is near the muzzle, so there
will be a little bit of recoil before the bullet exits, and it will be
greater with a lighter gun. It will be a pretty small effect though
since the change in center of mass is small, so your conclusion may
still be true.
klep...@aol.com
In article <5f5mal$l...@xring.cs.umd.edu>, Bret Jensen <bje...@willamette.edu> writes:
#Subject: [PHYSICS]: Recoil before bullet leaves barrel?
#From: Bret Jensen <bje...@willamette.edu>
#Date: 27 Feb 1997 23:18:29 -0500
#
#
## Put a 9-pound rifle with a 3-pound trigger burning twice or three times
## the powder behind three to four times the bullet weight in the hands of
## someone who isn't exactly holding the rifle the same for each shot and
## it's a different story. When free recoil energy goes from 3 pounds to 30
## pounds, there's going to be a lot more rifle movement before the bullet
## exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
#maintain their momentum unless acted upon. Until the bullet leaves the
#barrel there is no action to produce the "equal and opposite" reaction of
#recoil.
# I saw a series of high-speed strobe photos taken by Winchester in
#the 50s in which they had the muzzle of a Model 94 resting on a black
#block and a white sheet behind the rifle. With the bullet 1/2" out of
#the muzzle, there was no white space yet visible between the muzzle and
#block. With the bullet about 1 1/2 inch out of the muzzle, there was a
#thin white line visible between muzzle and block. The pictures were
#captioned, "Why felt recoil does not influence bullet strike," or
#something close to that.
#
#
# - Bret Jensen
#
#
#
The mass of the rifle is acted upon as soon as the bullet starts to move.
The rifle does not reach its peak velocity until after the bullet exits the muzzle
because: 1) the bullet is still accelerating and 2) the muzzle flash caused by
hot gases escaping also contribute (slightly) to the recoil energy.
No apparent movement of the rifle occurs due to the large difference in mass
between the bullet and rifle and the resulting large difference in velocity
between the two.
Kurt S. Lepinski
"They who can give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety." -- Benjamin Franklin
RDJ
Bret Jensen wrote:
#
# # Put a 9-pound rifle with a 3-pound trigger burning twice or three times
# # the powder behind three to four times the bullet weight in the hands of
# # someone who isn't exactly holding the rifle the same for each shot and
# # it's a different story. When free recoil energy goes from 3 pounds to 30
# # pounds, there's going to be a lot more rifle movement before the bullet
# # exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
# barrel there is no action to produce the "equal and opposite" reaction of
# recoil.
Strange, the physics *I* learned indicated momentum was a property of a
moving mass. "A body in motion tends to remain in motion...." Since
the firearm is (aside from shooter-shake) not moving at the time of
firing, there is no momentum at that moment; kinetic energy, maybe, but
no momentum. Physics being the ruler it is, at the instant a mass
begins to move, there is an immediate "equal and opposite" force
created. To assume, regardless of any "high-speed" photos, that this
force has no effect, is wrong. The ratio of bullet mass to firearm mass
is immense. The fact that there is little, if any, discernable movement
in the firearm before the bullet leaves the barrel has little meaning
because the acceleration of the firearm is much less than the
acceleration of the bullet due to this vast diffference in mass. When
looking at a lesser-weight firearm (a pistol) the movement becomes
obvious. Many modern, heavy-cartridge handguns have an unusually-high
front sight blade to help compensate for the muzzle rise during the time
the bullet is passing through the bore. "Hatcher's Notebook"
demonstrates the "jet-effect" claimed to further add to recoil velocity
during the moments after the bullet exits the muzzle. Although the
jet-effect cannot be discounted, the recoil effect begins virtually at
the moment the firing pin/hammer begins to move and increases as the
bullet is accelerated, then enhanced by the jet-effect. Recoil begins
immediately but the "felt recoil" takes a finite period to build, just
as the velocity of the bullet builds until the propellent is consumed or
the bullet exits the barrel.
--
"My problem lies in reconciling my gross habits with my net
income." -- Errol Flynn (and me too!)
Mike
Bret Jensen wrote:
#
# # Put a 9-pound rifle with a 3-pound trigger burning twice or three times
# # the powder behind three to four times the bullet weight in the hands of
# # someone who isn't exactly holding the rifle the same for each shot and
# # it's a different story. When free recoil energy goes from 3 pounds to 30
# # pounds, there's going to be a lot more rifle movement before the bullet
# # exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
# maintain their momentum unless acted upon. Until the bullet leaves the
# barrel there is no action to produce the "equal and opposite" reaction of
# recoil.
# block and a white sheet behind the rifle. With the bullet 1/2" out of
# the muzzle, there was no white space yet visible between the muzzle and
# block. With the bullet about 1 1/2 inch out of the muzzle, there was a
# thin white line visible between muzzle and block. The pictures were
# captioned, "Why felt recoil does not influence bullet strike," or
# something close to that.
#
# - Bret Jensen
BZZZT! Just exactly how do you suppose that the gun "knows" that the
bullet left the barrel? It doesn't, and it's irrelevant. The same
force pushing on the bullet is pushing in the opposite direction on the
gun, and at the same time.
That said: folks have suggested that the effects of "hold" are
essentially irrelevant, if the gun is being held by flesh. This is
allegedly due to the fact that human flesh can yield enough to "absorb"
the tiny movement of the gun while the bullet is still in the barrel.
So the gun is effectively "free" for the first bit of its travel, and
your hold is essentially irrelevant. This also allegedly explains why
strange things happen when you rest or brace a gun against a hard,
unyielding surface. However, I have no experience with this particular
effect.
I'm curious about this, and haven't done the math before, so let's see
how the numbers work out. For example: assume an 8 lb. bolt-action
rifle with 24 inch barrel, and a 150 grain bullet with a muzzle velocity
of 2700 fps. Upon exit, the rifle will be moving backward (if it's in
free space) at 7.2 fps. Assuming uniform acceleration (not a good
assumption, but it's easy to compute and pressure curves would suggest
that this gives us a worst-case answer), the bullet will have exited the
barrel in 1.48 mSec. The gun will have moved backwards .005 inches (.14
mm) in the same period of time. Again, this is probably a worst case
answer-- the actual movement is almost certainly less.
As another example, let's look at an example more representative of a
.416 Rigby. Let's say another 8 lb. gun and a 400 gr. bullet at 2400
fps from a 24" barrel. Bullet exits in 1.67 mSec. Gun is moving
backwards at 17.1 fps. Gun has moved backwards .014" when the bullet
exits. Indeed, it's nearly 3 times as much movement as in the other
case. But it's probably still insignificant.
Sounds like the "hold doesn't effect point of impact" theorists are
correct, at least with regard to recoil. Whether or not one's hold
affects barrel vibration is a completely different subject.
Mike
--
Mike Raley, Author of _Hidden In Plain Sight: A Practical Guide to
Concealed Handgun Carry_
For details: http://www.mindspring.com/~brco/brweb.htm
Bev Clark/Steve Gallacci
In article <5f5mal$l...@xring.cs.umd.edu>,
Bret Jensen <bje...@willamette.edu> wrote:
#
# COME ON. We all learned in high school physics that objects
#barrel there is no action to produce the "equal and opposite" reaction of
# I saw a series of high-speed strobe photos taken by Winchester in
#block and a white sheet behind the rifle. With the bullet 1/2" out of
#the muzzle, there was no white space yet visible between the muzzle and
#block. With the bullet about 1 1/2 inch out of the muzzle, there was a
#thin white line visible between muzzle and block. The pictures were
#captioned, "Why felt recoil does not influence bullet strike," or
#something close to that.
#
The recoil technically starts when the bullet starts moving, but with the
considerable inertia of the mass of the gun, and that the full "thrust"
of the moving bullet+gas doesn't happen until the bullet clears the muzzel,
there is a clear delay in felt recoil versus where the bullet is.
(and that a large portion of the recoil comes from the gas release at
extream velocity, rather than the bullet)
Daniel Morris DeRight
Excerpts from netnews.rec.guns: 27-Feb-97 [PHYSICS]: Recoil before bu..
by Bret Jensen@willamette.e
# # Put a 9-pound rifle with a 3-pound trigger burning twice or three times
# # the powder behind three to four times the bullet weight in the hands of
# # someone who isn't exactly holding the rifle the same for each shot and
# # it's a different story. When free recoil energy goes from 3 pounds to 30
# # pounds, there's going to be a lot more rifle movement before the bullet
# # exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
# maintain their momentum unless acted upon. Until the bullet leaves the
# barrel there is no action to produce the "equal and opposite" reaction of
# recoil.
If there's no change in momentum, what exactly makes the bullet
accerate from a dead stop to 3000+fps? What creates the backthrust that
can smear a head stamp? Certainly a reaction is occurring, and the
rifle is being pushed backwards, as the bullet moves forewards.
If your theory were true, then no recoil sould occur until the
bullet has left the barrel. If that were true, then a squib load where
the bullet got lodged in the barrel would not cause recoil, yet anyone
who has experienced one could tell you it does.
# I saw a series of high-speed strobe photos taken by Winchester in
# the 50s in which they had the muzzle of a Model 94 resting on a black
# block and a white sheet behind the rifle. With the bullet 1/2" out of
# the muzzle, there was no white space yet visible between the muzzle and
# block. With the bullet about 1 1/2 inch out of the muzzle, there was a
# thin white line visible between muzzle and block. The pictures were
# captioned, "Why felt recoil does not influence bullet strike," or
# something close to that.
Interesting, except that every bit of expericne I have says
otherwise. Recoil pads, muzzle brakes etc all lower the felt recoil,
and all dramatically effect where the bullet strikes. More than likely,
this evidence was due to improper testing conditions. What was the butt
of the rifle against? How fast was the camera taking pictures? If the
claim is that recoil and muzzle rise is mostly after the bullet exists,
I could certainly believe it, but I don't see how it could be possible
to accelerate something to 3000+fps without changing its momentum.
==========================
Dan DeRight sod...@cmu.edu
We do not read and write simply because it is enjoyable. We read and
write because we are part of humanity, and humanity is its story.
Bob Flyzik
#
# : # the powder behind three to four times the bullet weight in the hands of
# : # someone who isn't exactly holding the rifle the same for each shot and
# : # it's a different story. When free recoil energy goes from 3 pounds to 30
# : # pounds, there's going to be a lot more rifle movement before the bullet
# : # exits the muzzle.
#
# : COME ON. We all learned in high school physics that objects
# : maintain their momentum unless acted upon. Until the bullet leaves the
# : barrel there is no action to produce the "equal and opposite" reaction of
# : recoil.
# Not so. The gun begins moving backwards as soon as the bullet begins
# moving forward in the barrel. If the gun/bullet were at rest to begin
# with, total momentum is always zero until external forces on the gun
# (your shoulder) bring it back to rest. If a bullet has gained 1600 fps
# half-way down the barrel, the gun will already have rearward momentum
# which compensates the bullet's momentum. My Ph.D. is in physics.
#
# : the 50s in which they had the muzzle of a Model 94 resting on a black
# : block and a white sheet behind the rifle. With the bullet 1/2" out of
# : the muzzle, there was no white space yet visible between the muzzle and
# : block. With the bullet about 1 1/2 inch out of the muzzle, there was a
# : thin white line visible between muzzle and block. The pictures were
# : captioned, "Why felt recoil does not influence bullet strike," or
# : something close to that.
# This is more a matter of time than momentum. It only takes 0.001 seconds
# for a bullet to leave the barrel. Even though the gun begins moving rearward
# as soon as the bullet begins moving forward, it has not gone very far in the
# millisecond or so it takes for the bullet to be out of the barrel. For a
# 7.5 lb 30-06 shooting a 150 grain bullet, the rearward motion is roughly
# 0.07". With a much bigger gun, the momentum of the exhaust gasses play a
# much larger role, and combine with a larger bullet to produce a larger effect.
# I would estimate that in the time it takes a bullet to leave the barrel,
# a big game gun would move rearward roughly 0.21"
#
# The effect on recoil on accuracy depends not on the rearward motion but on
# the change in direction of the barrel as the bullet leaves. Conservation
# of angular motion must be used here because it is rotational motion that
# moves the barrel out of line. To compute this effect accurately requires
# knowing the moment of inertia of the gun about its pivoting axis. These
# parameters will vary widely depending on the gun and shooter. However, for
# a rough estimate, I will assume that the barrel jumps up 5% of the amount
# the rifle moves backward, or 0.007" for a 30-06 and 0.021" for a big game gun.
# This effect produces a 0.5 MOA deflection in a 30-06 and a 1.5 MOA deflection
# in the big game gun.
#
# A person's strength is not nearly as important in reducing this effect as
# the way they were holding the gun when they pulled the trigger, because
# it's the way the gun is held and it's moment of inertia that determine
# its pivoting axis. Usually, the pivoting axis is below the line of the
# barrel bore, which is why the barrel moves up. If the pivoting axis
# is on the bore line, then the angular momentum of the gun remains zero
# and the gun doesn't move.
#
# --
# Michael Courtney, Ph. D.
# mic...@amo.mit.edu
#
#
Right on doc! I was pretty upset with a .44 Magnum revolver I was
sighting in at the range...even though I had the butt of the gun resting
on the bench, all my hits were high, even after cranking the sights all
the way down. When it was time to leave, I had a cylinder full of
rounds left, so I cranked them off from a standing, two-handed position,
unsupported by the bench. They were nicely grouped in the bulls-eye.
Bob Flyzik, MSgt
I took Physics in high school
Bryce Mohan
# COME ON. We all learned in high school physics that objects
#barrel there is no action to produce the "equal and opposite" reaction of
#recoil.
# I saw a series of high-speed strobe photos taken by Winchester in
#block and a white sheet behind the rifle. With the bullet 1/2" out of
#the muzzle, there was no white space yet visible between the muzzle and
#block. With the bullet about 1 1/2 inch out of the muzzle, there was a>
#thin white line visible between muzzle and block. The pictures were
#captioned, "Why felt recoil does not influence bullet strike," or
#something close to that.
#
#
# - Bret Jensen
I think your talking about muzzle flip not recoil. I'm no physics expert but it would
seem the force of the gases propelling the bullet down the barrel would be acting on
the barrel in a reverse direction simaltaneously.
Ken Marsh
Hi,
Jim Nasset <a...@inventorworld.com> wrote:
#Boy, you have opened a can of worms now. About a year ago I attempted to
#explain to a number of "disbelievers" in the group that any (rearward)
#rifle movement from recoil prior to the exit of the bullet from the muzzle
#was insignificant.
For most modern high velocity rifles, this is true enough. For .45-70 and
cartridges with even heavier bullets, long barrels and slower
velocities, time-in-bore becomes an issue. Recoil occurs enough to
affect trajectory.
There are a few military rifles, I think one of the Lee Enfields was one
of them, that shoots different weight bullets to the same point of
impact (up to a point). The reason was that the recoil of the heavier
bullets caused a corresponding increase in muzzle rise, to the exact
level needed to compensate for the increased drop of the slower bullet.
This felicity of design was accidental, but welcome.
There is a simple test to prove you wrong, though. Shoot a light .30-06
bolt gun from a bench using your normal hold. Then do it again, touching
the gun with only your fingertip (no shoulder hold at all, be sure and
catch the flying gun :). Notice how the point of impact changes
measurably.
Repeat the test with a heavy barrel 222, and you'll see only a very
little change in impact, which demonstrates my point.
#This is simply because the mass of the bullet and powder
#moving down the barrel is insufficient to overcome the many times greater
#at rest mass of the rifle. Because of the riflings however, there is a
#small rotational force attempting to twist the rifle in the opposite
#direction of the twist direction. This twist however would be essentially
#the same for each bullet (traveling at substantially the same speed and
#with the same bearing surface) therefore once the sights had been initially
#adjusted, this cant is made up for. But get ready for a bunch of "opinions"
#to the contrary.
Some JDJ pistol shooters, and maybe a few light .44Mag shooters have
experienced this twist to the point that it hurts the wrist. There is
also the Magnus effect, but few of us (outside of 1,000 yard Springfield
trapdoor and 155mm Howitzer shooters :) have to worry about that.
You're correct in so far that, for MOST shooters, it just doesn't matter.
Ken
--
-------------------------------------------------------------------------
Mail: kma...@charm.net | Edit a binary .INI file, then tell
WWW: http://www.charm.net/~kmarsh | me that UNIX is too complicated.
-------------------------------------------------------------------------
Bartbob
I well understand what you're talking about. And I saw the '50s stuff
about the strobe photos of a bullet leaving the barrel. Yes, the barrel
didn't move up very much. But if the muzzle only moved up five thousandths
of an inch and the breech didn't move up at all, that's enough to move
bullet impact up about 1 MOA from where it would have struck had the
barrel not moved up at all.
I agree, the amount of "felt" recoil won't effect bullet impact. As most
(90% or more) recoil happens after the bullet leaves the barrel, one would
be hard pressed to "feel" recoil while the bullet's in the bore.
But there definitely is an effect on recoil energy effecting how far the
barrel moves while the bullet is going down it. Virtually all of that
movement is straight back; very little is in the vertical plane.
For example, there can be 100 fps or more average muzzle velocity for a
given rifle and ammo depending on how firm the rifle is held. The harder
it's held, the higher muzzle velocity is. One can easily find this out
with an accurate chronograph.
There's a higher muzzle velocity from the prone position where the rifle
is solidly held compared to offhand or standing where the rifle has much
less support.
A friend of mine and I were testing a 30 caliber magnum's loads some years
ago.
He consistantly got about 110 fps higher average muzzle velocity than I.
We swapped the rifle between us 4 times for ten shots each; all with the
same ammo. He weighed about 280 pound; a really big person who held rifles
very tightly. I, at about 190 pounds and not holding the rifle as tight
as he naturally got the lower muzzle velocities. Interestingly enough,
rifle muzzle velocities from machine rests will have a lower spread than
when the rifle is held in position. The reason is that the resistance to
recoil is the same from shot to shot with a machine rest; but that
resistance varies as us mortals hold the rifle for each shot.
And top competitive shooters well know that in the prone position, if the
shots are well centered in the bullseye, then the forward elbow is moved
an inch or so, in any direction, the shots fired after moving the elbow
will shoot just as accurate, but the group center is displaced by as much
as 1 MOA; sometimes more. The more recoil energy there is when this
happens, the further the group will move. With the same amount of elbow
movement, a 30 caliber magnum will have its group center moved 2 to 3
times as much as a .22 centerfire.
Although the rifle movement backwards during the bullet's flight down the
barrel is small, it is enough to effect where the muzzle points when the
bullet exits. Physics says there has to be some rearward movement; and
there is some.
There's even some twisting due to the rifling acting on the bullet.
Again, it's not very much, but it's been observed by competitive shooters
with magnums. I've observed it myself. The scope's reticule appears to
twist counter-clockwise with right-hand rifling twist.
Even with a 13-pound .22 rimfire smallbore match rifle zeroed in a machine
rest, the sights will be off compared to what they need to be set at when
the rifle is shot in position. .22 rimfire's have little recoil energy,
but enough to require sight changes to center up. There's a greater
difference with centerfire match rifles zeroed in machine rests, then shot
off the shoulder at the same distance because the recoil energy is higher.
I can well understand why most folks don't believe what I've mentioned
above. But just because one doesn't believe it does not mean it doesn't
happen.
BB
Bill Oertell
How recoil affects the POI has absolutely nothing to do with how far
backwards the firearm moves. It has to do with the angle between the
rifle and the point(s) of resistance behind it.
A free-floating rifle will recoil straight back...no muzzle rise at
all. However, a rifle pressed up into your shoulder will most
definitely rise a little before the bullet leaves the muzzle, unless the
shoulder is directly behind the line of the barrel.
If the point of resistance (the fulcrum, actually) is at any angle
to the barrel, there will be some vector force that causes the muzzle to
rise. This is not an opinion, it is a fact.
Bill
Andykun66
I haven't done much testing with rifles on this subject, but it can be
easily observed with handguns. My S&W 1917 revolver, in .45 ACP, will
strike to point of aim with 230 gr. bullets at 25 yds. With 185 gr., it is
a good 6 inches low. If I load those aformentioned 230 grainers for 100
fps. less muzzle velocity, they hit 2 inches higher. What this is telling
me is the gun is recoiling while the bullet is still in the barrel. Is
this a reasonable conclusion?
The T/C contender is another example of this. It dosen't matter
what caliber barrel I have on it, if I allow the grip to touch anything -
the top of the bench or my hand, it will string its shots vertically. If I
put the forend on the sandbags and snug the front of the trigger guard up
into the bag, it becomes a different gun entirely, and groups become round
and much smaller. If the gun didn't move until the bullet had exited the
barrel, it wouldn't matter, right?
Let's hear some more comments on this - it's getting interesting!
Andy O.
Bill Oertell
# This is more a matter of time than momentum. It only takes 0.001 seconds
# for a bullet to leave the barrel. Even though the gun begins moving rearward
# as soon as the bullet begins moving forward, it has not gone very far in the
# millisecond or so it takes for the bullet to be out of the barrel. For a
# 7.5 lb 30-06 shooting a 150 grain bullet, the rearward motion is roughly
# 0.07". With a much bigger gun, the momentum of the exhaust gasses play a
# much larger role, and combine with a larger bullet to produce a larger effect.
# I would estimate that in the time it takes a bullet to leave the barrel,
# a big game gun would move rearward roughly 0.21"
#
I once calculated the muzzle rise of a .44 mag with 6" barrel at .1
inches as the bullet leaves the muzzle. I did NOT factor in the weight
of the shooter's hands, which would have to be included. I also only
considered the angle between the center of the shooter's hands and the
center of the barrel. It would have been too complicated otherwise, and
I don't think the ommision of the other angles involved (gun to elbow,
gun to shoulder) is nearly as significant as the angle between the grip
and the barrel.
Considering the fact that barrel vibrations can effect rifle
accuracy, it would take little muzzle rise in a rifle to do the same. I
imagine there'd even be a difference of POI between standing and bench,
though I think it'd be less than the margine of error introduced by a
standing shooting position. (Well, at least for me, anyway).
Bill
Walter Taylor
## the powder behind three to four times the bullet weight in the hands of
## someone who isn't exactly holding the rifle the same for each shot and
## it's a different story. When free recoil energy goes from 3 pounds to 30
## pounds, there's going to be a lot more rifle movement before the bullet
## exits the muzzle.
#
#maintain their momentum unless acted upon. Until the bullet leaves the
#barrel there is no action to produce the "equal and opposite" reaction of
#recoil.
# I saw a series of high-speed strobe photos taken by Winchester in
#the 50s in which they had the muzzle of a Model 94 resting on a black
#block and a white sheet behind the rifle. With the bullet 1/2" out of
#the muzzle, there was no white space yet visible between the muzzle and
#block. With the bullet about 1 1/2 inch out of the muzzle, there was a
#thin white line visible between muzzle and block. The pictures were
#captioned, "Why felt recoil does not influence bullet strike," or
#something close to that.
#
#
# - Bret Jensen
#
I believe you mis-interpret the physics of the situation. The force,
excelleration of the bullet/powder gas only occures while in the tube.
As the bullet/gas leaves the muzzle all weapon action-reactions stop
and only momentum in the firearm remains so maximum recoil velocity
has been achieved and only the deceleration of this velocity remains.
My only explaination of what the photo showed was that the time required
to achieve full recoil velocity is small hence the distance travled
was less than photo resolution.
wait
Jeffrey A. Del Col
#
#
#Bret Jensen <bje...@willamette.edu> wrote in article
#<5f5mal$l...@xring.cs.umd.edu>...
##
## # Put a 9-pound rifle with a 3-pound trigger burning twice or three times
## # the powder behind three to four times the bullet weight in the hands of
## # someone who isn't exactly holding the rifle the same for each shot and
## # it's a different story. When free recoil energy goes from 3 pounds to
#30
## # pounds, there's going to be a lot more rifle movement before the bullet
## # exits the muzzle.
##
## COME ON. We all learned in high school physics that objects
## maintain their momentum unless acted upon. Until the bullet leaves the
## barrel there is no action to produce the "equal and opposite" reaction of
#
## recoil.
#
Ummm... are you saying that Newton's laws are "on hold" until
the bulllet leaves the barrel?
Once the bullet/propellant combination's force exceeds the
rest inertia of the rifle, the firearm will move, and
and this point occurs before the
bullet leaves the barrel. If it doesn't, there will be no--felt--
recoil at all. The bullet de-celerates once it leaves the barrel.
Newton's laws are in force all the time, and the reaction
begins the instant the bullet moves.
Human physiology being what it is, our nervous system is "slower than
a speeding bullet," so the actual effect of recoil on accuracy
is close to nil.
Unless, of course, the shooter anticipates the recoil and flinches.
J. Del Col
--
Jeff Del Col * "Sleeplessness is like metaphysics.
A-B College * Be there."
Philippi, WV *
* ----Charles Simic----
dbco...@ipass.net
In article <5f5mal$l...@xring.cs.umd.edu>, bje...@willamette.edu says...
#
#
## Put a 9-pound rifle with a 3-pound trigger burning twice or three times
## the powder behind three to four times the bullet weight in the hands of
## someone who isn't exactly holding the rifle the same for each shot and
## it's a different story. When free recoil energy goes from 3 pounds to 30
## pounds, there's going to be a lot more rifle movement before the bullet
## exits the muzzle.
#
# COME ON. We all learned in high school physics that objects
#maintain their momentum unless acted upon. Until the bullet leaves the
#barrel there is no action to produce the "equal and opposite" reaction of
#recoil.
# I saw a series of high-speed strobe photos taken by Winchester in
#the 50s in which they had the muzzle of a Model 94 resting on a black
#block and a white sheet behind the rifle. With the bullet 1/2" out of
#the muzzle, there was no white space yet visible between the muzzle and
#block. With the bullet about 1 1/2 inch out of the muzzle, there was a
#thin white line visible between muzzle and block. The pictures were
#captioned, "Why felt recoil does not influence bullet strike," or
#something close to that.
#
#
Well Bret... the reason the rise may not have been apparent in the
film is the very minimal amount of rise...
For a simplistic view consider the following:
Assume:
a rise to cause 1 MOA deflection at 100 yds...
a rifle 36 inches long...
butt against stop...
Rise at muzzle EQUALS 0.010 inches...
Which begs the question... was the resolution capability of a 50's
quality camera able to see a few thousands of an inch... was the camera close
enough to show it...
If Bret is right then the po ol Lyman company has been full of crap
all these years in their 'Accuracy Tips & Techniques' article... of course
they wouldn't know anything about this subject... ;-)
Now to really stir things up... Lyman says that you can actually get
a NEGATIVE 'muzzle jump' in certain firearm designs, most particularlly some
gas operted firearms... heheheheheheehe....
db 'who loves a good techie discussion' cooper
Larry Bump
#Bret Jensen <bje...@willamette.edu> wrote in article
## COME ON. We all learned in high school physics that objects
## maintain their momentum unless acted upon. Until the bullet leaves the
## barrel there is no action to produce the "equal and opposite" reaction of
## recoil.
Well, that time I loaded the .44 with Unique to Bullseye data
(thankfully not the other way around!),
the bullet wedged in the barrel.
There WAS a noticeable recoil impulse, though obviously not very much.
The bullet is stable relative to the firearm prior to ignition. After
ignition but before "barrel/bullet separation" there is a significant
change in their relative positions and velocities, though the bullet
is still covered by the bullet. Wherefor dost thou say there has been
no action?
Jim Gaspar
Bill Oertell <woer...@ix.netcom.com> wrote in article
<5f9iih$1...@xring.cs.umd.edu>...
# I once calculated the muzzle rise of a .44 mag with 6" barrel at .1
# inches as the bullet leaves the muzzle. I did NOT factor in the weight
# of the shooter's hands, which would have to be included. I also only
# considered the angle between the center of the shooter's hands and the
# center of the barrel. It would have been too complicated otherwise, and
# I don't think the ommision of the other angles involved (gun to elbow,
# gun to shoulder) is nearly as significant as the angle between the grip
# and the barrel.
...
# Bill
#
It isn't just the 'weight' of the hands, it's how the gun is 'held'. To
correcly model how a firearm
will behave when a round is discharged, you need to model how the firearm
is restrained. Real life
constraints can be as complictated as you want, depending on the accuracy
you want. As a start,
I would model the entire human body, including the lengths and weights of
the various limbs and
also(!) the *tension* in the constraints to the limbs (the muscles) and the
'crushiness' of human flesh
and any glove or shirt or other clothing that was between the firearm and
the body. A couple simpler
models would be a 'free' floating firearm, with no one holding it, a fiream
encased in a concrete pillar
weighing 300 pounds or, slightly more complicated, a ransom rest.
If this seems too simple, then try to answer the question "which cartridges
have the most painful
recoil?" Then you get to add the way pain is felt by the body and how it
varies between individuals.
If you mulitply the max pressure in psi that a certain load produces in a
firearm and mulitply it by
the inside area of the cartridge base in sq. in., you can calculate the
maximum force being
exerted rearward along the axis of the barrel. Good thing it's over quick!
Dan Brown
andy...@aol.com (Andykun66) wrote:
# fps. less muzzle velocity, they hit 2 inches higher. What this is telling
# me is the gun is recoiling while the bullet is still in the barrel. Is
# this a reasonable conclusion?
IMHO, that isn't a reasonable conclusion, because the data
you've given support another conclusion just as strongly (if not more
so)--trajectory varies with velocity, after all.
# Let's hear some more comments on this - it's getting interesting!
OTOH, physics-wise, it's a no-brainer to conclude that _some_
recoil happens before the bullet leaves the barrel--there is a clearly
a force acting on the bullet, so there _must_ be an equal and opposite
reaction.
--
Dan Brown, KE6MKS, da...@value.net
Finger bro...@holmes.uchastings.edu for public key & Geek Code
E-Mail published at my discretion.
Lon Lentz
Bret Jensen <bje...@willamette.edu> wrote:
# COME ON. We all learned in high school physics that objects
#maintain their momentum unless acted upon. Until the bullet leaves the
#barrel there is no action to produce the "equal and opposite" reaction of
#recoil.
Recoil is the "opposite" reaction to the action of the bullet moving
down the barrel. As the expanding gasses "force" the bullet down the
barrel, they "force" the rifle back into your shoulder equally.
The recoil force is applied for such a short period of time, it
could be called an impulse. Where the Impulse, J, is equal to the
"constant" force multiplied by the time it takes the bullet to
traverse the barrel.
Considering the ignition pressures of the loads, and the total
internal volume of a barrel, I think it would be safe to assume that
the pressure "remains constant". And what is the time it takes the
bullet to traverse the barrel? A lot less than a second. (I have no
real numbers to plug in here.)
This is equal to the mass of the bullet times its velocity change.
Since the bullet mass is small (we're talking in lbs/kgs here), we can
drop it and the time. This gives us something where the recoil force
is related/equal/proportional to the bullet's change in velocity.
=> J = F(t2-t1) = m(v2-v1)
The only acceleration the bullet does is in the barrel. It's the
only time possible for the "opposite" recoil force.
Anyone here ever shoot a squib and not know it?
There is also the re-igniting gas at the muzzle that adds to this
recoil at the end. And from the way these muzzle brakes work, I would
guess this force to be somewhat comparable to the "accelerating
recoil" in some casses.
Digital Armaments Corporation
Arming You for the Digital Revolution!
www.digitalarms.com
Jeffrey A. Del Col
In a previous article, a...@inventorworld.com (Jim Nasset) says:
#
#
#
#
#
#Boy, you have opened a can of worms now. About a year ago I attempted to
#explain to a number of "disbelievers" in the group that any (rearward)
#rifle movement from recoil prior to the exit of the bullet from the muzzle
#was insignificant. This is simply because the mass of the bullet and powder
#moving down the barrel is insufficient to overcome the many times greater
#at rest mass of the rifle.
Are you saying that the bullet/ propellant mass-- increases-- when
the bullet leaves the barrel? That's nonsense.
The relevant formula is F=MA. Once the bullet starts to accelerate, so does
the rifle. When the bullet/propellant mass accelerates
to the point at which it overcomes the inertia of the rifle, the rifle
will move perceptibly. This must happen before the bullet
leaves the barrel. Bullets de-celerate when they leave the barrel because
the thrust behind them effectively drops to zero.
It may take a bit longer for the mass of the shooter to get moving, but
that's another problem. The recoil force has to peak before the
bullet leaves the barrel.
If a rifle were fired in free fall in a vacuum, the immediate acceleration
due to recoil would be obvious.
Louis Boyd
Walter Taylor wrote:
#
# Bret Jensen <bje...@willamette.edu> wrote:
# # COME ON. We all learned in high school physics that objects
# #maintain their momentum unless acted upon. Until the bullet leaves the
# #barrel there is no action to produce the "equal and opposite" reaction of
# #recoil.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
better take that course over again.
# # I saw a series of high-speed strobe photos taken by Winchester in
# #the 50s in which they had the muzzle of a Model 94 resting on a black
# #block and a white sheet behind the rifle. With the bullet 1/2" out of
# #the muzzle, there was no white space yet visible between the muzzle and
# #block. With the bullet about 1 1/2 inch out of the muzzle, there was a
# #thin white line visible between muzzle and block. The pictures were
# #captioned, "Why felt recoil does not influence bullet strike," or
# #something close to that.
# #
# #
# # - Bret Jensen
# #
# #
# I believe you mis-interpret the physics of the situation. The force,
# excelleration of the bullet/powder gas only occures while in the tube.
# As the bullet/gas leaves the muzzle all weapon action-reactions stop
# and only momentum in the firearm remains so maximum recoil velocity
# has been achieved and only the deceleration of this velocity remains.
# My only explaination of what the photo showed was that the time required
# to achieve full recoil velocity is small hence the distance travled
# was less than photo resolution.
I have to agree with Walt on this on. If your interested in this
subject
Col. Julius Hatcher has a chapter on this subject in his book "Hatcher's
Notebook". He uses the example of the example of an 8.69 lb rifle, a
150gn
bullet, and 50 gn of powder, with an effective barrel length (bullet
travel)
of 21.597 inches. In this example the rifle moves .06183 inches as the
bullet travels the length of the barrel. The velocity is not required
for
the calculation, although there is a small assumption of the
distribution of
gasses in the barrel. In the example Hatcher was using the bullet
traversed
the barrel in slightly under 1 millisecond.
The situation which Bret described would only be true if the bullet were
bonded to the case and didn't move. Once the bullet begins to move the
rifle MUST move rearward to keep the center of mass of the system
(gas,powder
bullet,air, shooter, target, and earth) at it's original position. (yes,
it's
true, the center of mass doesn't move!)
Whether the photo should resolve a .06" movement parallel to the bore I
can't say.
The rifle is accelerating during the time the bullet is in the barrel
and
for a very short amount of time afterward as the remaining gas exits the
barrel. From that point on the rifle decelerates as it transfers the
momentum
to the shooter and then the earth (or benchres/bench/earth).
As to affecting accuracy, anything which effectively adds (or removes)
mass
to the rifle is likely to affect it's point of aim. A typical rifle
isn't
symetrical and gains rotational momentum as it is fired. (muzzle flip).
Adding mass to the stock (like having a shoulder there) will cause it to
shoot slightly higher than in free recoil. The effect is small because
the shoulder and padding are soft and don't add much effective mass in
the .06" that the rifle travels. Nonetheless,an inconsistant hold will
cause
a detectable effect on accuracy.
Paul J Ruiz
Bill:
" A free-floating rifle will recoil straight back...no muzzle rise at
all. However, a rifle pressed up into your shoulder will most
definitely rise a little before the bullet leaves the muzzle, unless the
shoulder is directly behind the line of the barrel.
If the point of resistance (the fulcrum, actually) is at any angle
to the barrel, there will be some vector force that causes the muzzle to
rise. This is not an opinion, it is a fact."
May I inject a refinement to the statement about the free_floating
rifle? The statement is true only IF the center of gravity is in line
with the bore. The center of gravity would in effect be the fulcrum,
albeit a "soft" one.
Paul
Jeffrey A. Del Col
In a previous article, bev...@netcom.com (Bev Clark/Steve Gallacci) says:
[A
##the muzzle, there was no white space yet visible between the muzzle and
##block. With the bullet about 1 1/2 inch out of the muzzle, there was a
##thin white line visible between muzzle and block. The pictures were
##captioned, "Why felt recoil does not influence bullet strike," or
##something close to that.
##
#Not quite.
#The recoil technically starts when the bullet starts moving, but with the
#considerable inertia of the mass of the gun, and that the full "thrust"
#of the moving bullet+gas doesn't happen until the bullet clears the muzzel,
#there is a clear delay in felt recoil versus where the bullet is.
#(and that a large portion of the recoil comes from the gas release at
#extream velocity, rather than the bullet)
Are you saying that the propellant gases are accelerating
faster than the bullet --in front-- of them? Or that the propellant
has a greater mass than the bullet? This latter is true only
in experimental loads using huge powder charges with very light
bullets. By far the greatest proportion of recoil is generated
by the bullet's acceleration. Fire a few blanks, and you'll see what
I mean.
Keith Wood
In article <5fc5vr$6...@xring.cs.umd.edu>,
br...@cleveland.Freenet.Edu (Jeffrey A. Del Col) wrote:
[
[In a previous article, a...@inventorworld.com (Jim Nasset) says:
[
[#Boy, you have opened a can of worms now. About a year ago I attempted to
[#explain to a number of "disbelievers" in the group that any (rearward)
[#rifle movement from recoil prior to the exit of the bullet from the muzzle
[#was insignificant. This is simply because the mass of the bullet and powder
[#moving down the barrel is insufficient to overcome the many times greater
[#at rest mass of the rifle.
[
[
[Are you saying that the bullet/ propellant mass-- increases-- when
[It may take a bit longer for the mass of the shooter to get moving, but
[that's another problem. The recoil force has to peak before the
[bullet leaves the barrel.
No. You are assuming that recoil is solely from the mass/veslocity
of the bullet, which ignoes the GREATEST component of recoil:
THRUST.
When you fire a rifle, the bullet is propelled by an expanding mass
of propellant gasses. Once the bullet leave the muzzle, those gasses
are released to the outside. They then provide thurst in the same
manner as a rocket engine, and in fact a solid-fuel rocket is nothing
more than a cartridge with no projectile.
[If a rifle were fired in free fall in a vacuum, the immediate acceleration
[due to recoil would be obvious.
Yes -- and less than firing that same round in the atmosphere.
There are two components to the thrust from the muzzle, mass-reaction
(the movement of mass, including the expanding propellant gasses] and
aerodynamic pressure (as the expanding could of gas pushes against
the outside air while still at a high pressure in the bore).
The aerodynamic component is familiar to all shooters as "muzzle
blast" and also includes oft oft-forgotten back pressure of forcing
the ambient atmosphere out of the bore AHEAD OF THE BULLET).
Steve Spoldi
Gentlemen,
I believe simple conservation of momentum can be applied, i.e. bullet
mass * bullet velocity = firearm mass * recoil velocity. This also
applies to the position displacement, bullet mass * barrel length =
firearm mass * change in position (while the bullet is in the barrel).
The same gas pressure that pushes the bullet down the barrel pushes the
firearm backwards. Does anyone agree?
Sincerely, Steve S.
Bill Oertell
# May I inject a refinement to the statement about the free_floating
# rifle? The statement is true only IF the center of gravity is in line
# with the bore. The center of gravity would in effect be the fulcrum,
# albeit a "soft" one.
Hmm...good point.
Bill
Walter Taylor
kei...@bctv.com (Keith Wood) wrote:
#In article <5fc5vr$6...@xring.cs.umd.edu>,
#br...@cleveland.Freenet.Edu (Jeffrey A. Del Col) wrote:
#[
#[In a previous article, a...@inventorworld.com (Jim Nasset) says:
#[
#[#Boy, you have opened a can of worms now. About a year ago I attempted to
#[#explain to a number of "disbelievers" in the group that any (rearward)
#[#rifle movement from recoil prior to the exit of the bullet from the muzzle
#[#was insignificant. This is simply because the mass of the bullet and powder
#[#moving down the barrel is insufficient to overcome the many times greater
#[#at rest mass of the rifle.
#[
#[
#[
#[Are you saying that the bullet/ propellant mass-- increases-- when
#[the bullet leaves the barrel? That's nonsense.
#
#[It may take a bit longer for the mass of the shooter to get moving, but
#[that's another problem. The recoil force has to peak before the
#[bullet leaves the barrel.
#
#No. You are assuming that recoil is solely from the mass/veslocity
#of the bullet, which ignoes the GREATEST component of recoil:
#
#THRUST.
#
#When you fire a rifle, the bullet is propelled by an expanding mass
#of propellant gasses. Once the bullet leave the muzzle, those gasses
#are released to the outside. They then provide thurst in the same
#manner as a rocket engine, and in fact a solid-fuel rocket is nothing
#more than a cartridge with no projectile.
#
#[If a rifle were fired in free fall in a vacuum, the immediate acceleration
#[due to recoil would be obvious.
#
#Yes -- and less than firing that same round in the atmosphere.
#
#There are two components to the thrust from the muzzle, mass-reaction
#(the movement of mass, including the expanding propellant gasses] and
#aerodynamic pressure (as the expanding could of gas pushes against
#the outside air while still at a high pressure in the bore).
#
#The aerodynamic component is familiar to all shooters as "muzzle
#blast" and also includes oft oft-forgotten back pressure of forcing
#the ambient atmosphere out of the bore AHEAD OF THE BULLET).
#
You miss the cause of the thrust effect. Thrust is mass of the gas
times the velocity of that gas. The effective velocity of gun power
gases are approximated at something on the order of 5000 fps on
exiting the muzzle, an indicator of the practial limitation of bullet
velocity for a single stage weapon. Do not have references handy but
I believe it was Hatcher.
wait
Keith Wood
In article <5fc5vr$6...@xring.cs.umd.edu>,[[
[#Boy, you have opened a can of worms now. About a year ago I attempted to
[
[
[Are you saying that the bullet/ propellant mass-- increases-- when
[It may take a bit longer for the mass of the shooter to get moving, but
[that's another problem. The recoil force has to peak before the
[bullet leaves the barrel.
No. You are assuming that recoil is solely from the mass/veslocity
of the bullet, which ignoes the GREATEST component of recoil:
THRUST.
When you fire a rifle, the bullet is propelled by an expanding mass
of propellant gasses. Once the bullet leave the muzzle, those gasses
are released to the outside. They then provide thurst in the same
manner as a rocket engine, and in fact a solid-fuel rocket is nothing
more than a cartridge with no projectile.
[If a rifle were fired in free fall in a vacuum, the immediate acceleration
[due to recoil would be obvious.
Yes -- and less than firing that same round in the atmosphere.
There are two components to the thrust from the muzzle, mass-reaction
(the movement of mass, including the expanding propellant gasses] and
aerodynamic pressure (as the expanding could of gas pushes against
the outside air while still at a high pressure in the bore).
The aerodynamic component is familiar to all shooters as "muzzle
blast" and also includes oft oft-forgotten back pressure of forcing
James Del Vecchio
Mike <mra...@gi.com> wrote:
#That said: folks have suggested that the effects of "hold" are
#essentially irrelevant, if the gun is being held by flesh. This is
#allegedly due to the fact that human flesh can yield enough to "absorb"
#the tiny movement of the gun while the bullet is still in the barrel.
#So the gun is effectively "free" for the first bit of its travel, and
#your hold is essentially irrelevant. This also allegedly explains why
My wife is a lefty, and pistols consistantly shoot to a different
point of aim for her. A Colt's Dect. Spl, with fixed sights has
always shot a frustrating half foot (it seems anyway) left for me
at 7 yds, but it's right on for her. Ditto for her Blackhawk.
My stuff is off for her, also.
JD
Tom Jennings
Keith Wood wrote:
#
# In article <5fc5vr$6...@xring.cs.umd.edu>,
# br...@cleveland.Freenet.Edu (Jeffrey A. Del Col) wrote:
# [
# [In a previous article, a...@inventorworld.com (Jim Nasset) says:
# [
# [#Boy, you have opened a can of worms now. About a year ago I attempted to
#
#
# [If a rifle were fired in free fall in a vacuum, the immediate acceleration
# [due to recoil would be obvious.
#
# Yes -- and less than firing that same round in the atmosphere.
#
e
Hoo-boy:
A can of worms, indeed! I believe that the propellant gas escapes at
about 4x the bullets velocity. Square 4 the propellant charge vs. the
weight of the bullet and you will get some suprising figures.
I still believe Newton. When the bullet starts to move forward, the gun
must start back. Right then and now.
Anyone who has a .45 will see that if he loads 185gr. and 230 gr loads
for the same pistol. The 185's shoot lower . The barrel rise is
dependent on the mass of the pistol, the grip, and how the pistol is
rested. As the lighter bullet leaves faster, the slower muzzle rise
puts the impact lower.
As the variables of gun mass, grip, and even body mass of the shooter
change, the reaction will vary.
TC Contenders are a different story. A low mass .45LC barrel is a good
example of the horrible results when you change bullet weights and
velocities. The wide variety of handloads make sighting in veeery
interesting.
A 14" scoped ,30-.30 shows some of this effect, but is moderated by
heavy barrell and scope.
Tom
Ken Marsh
In article <5fc654$6...@xring.cs.umd.edu>, Dan Brown <da...@value.net> wrote:
#andy...@aol.com (Andykun66) wrote:
#
## fps. less muzzle velocity, they hit 2 inches higher. What this is telling
## me is the gun is recoiling while the bullet is still in the barrel. Is
## this a reasonable conclusion?
#
# IMHO, that isn't a reasonable conclusion, because the data
#you've given support another conclusion just as strongly (if not more
#so)--trajectory varies with velocity, after all.
Except that impact point usually RISES with velocity, but velocity
was falling, and so was the bullet. It is a reasonable conclusion.
And, being a pistol, I don't think it was barrel whip.
Ken.
Robert T. Haas
Louis Boyd wrote:
#[snipped]
# As to affecting accuracy, anything which effectively adds (or removes) mass
# to the rifle is likely to affect it's point of aim. A typical rifle isn't
# symetrical and gains rotational momentum as it is fired. (muzzle flip).
# Adding mass to the stock (like having a shoulder there) will cause it to
# shoot slightly higher than in free recoil. The effect is small because
# the shoulder and padding are soft and don't add much effective mass in
# the .06" that the rifle travels. Nonetheless,an inconsistant hold will
# cause a detectable effect on accuracy.
Since the rifle is supported by the right shoulder (for a right-handed
shooter) there should also be a small rotational moment to the right,
the moment would be to the left for a left-handed shooter.
Robert T. Haas
Jim Nasset
Steve Spoldi <spo...@worldnet.att.net> wrote in article
<5fcpsl$8...@xring.cs.umd.edu>...
# Gentlemen,
# I believe simple conservation of momentum can be applied, i.e. bullet
# mass * bullet velocity = firearm mass * recoil velocity. This also
# applies to the position displacement, bullet mass * barrel length =
# firearm mass * change in position (while the bullet is in the barrel).
# The same gas pressure that pushes the bullet down the barrel pushes the
# firearm backwards. Does anyone agree?
#
# Sincerely, Steve S.
Yes, the gas pressure reacts against the rifle when it is released at the
muzzle.
The often quoted statement is "for each action there is an equal and
opposite reaction" which of course is true. The one not mentioned here is
"a body at rest tends to remain at rest" which when both of these are
applied using the formula F=MA you will quickly understand why, until the
escaping gas leaves the muzzle, that there is insignificant reward motion
of the rifle.
The mass of a 168 grain bullet combined with the mass of 45 grains of
powder is 0.0009461. The velocity of the bullet from a 26 inch barrel is
2650 fps. And the weight of my .308 Rem VS including scope is 10.5 pounds
and its mass is 0.3264925.
The force acting against the rifle caused by the acceleration of the bullet
and powder down the barrel can then be calculated using the above
parameters.
Force = 0.0009461 times 2650 fps times .01 seconds (the time it takes the
bullet to traverse the barrel)
Force = 2.507165 pounds times .01 sec
Force = 0.02507 foot pounds.
So what we have is 0.02407 foot pounds attempting to move an "at rest mass"
of 10.5 pounds, sorry, but it is not going to happen. This also does not
take into account the friction of the bearing surface of the bullet
attempting to pull the rifle forward, or the friction between the stock and
the sandbag, or the resistance of the mass of the upper body of a man,
restricting the reward movement.
A simple test you can perform to duplicate the reaction of your rifle to
this applied force, is to take a "very sensitive" pull gage, attach it to
the butt, or trigger guard of your rifle while it is laying on a sand bag
and apply 0.024077 pounds of pull to it and measure the distance the rifle
moved. (Not much, was it.)
If it were not true that the force needed to overcome an at rest mass must
be more than the mass itself, every time a volcano erupted on earth, or a
rocket was launched, the earth would be moved (albeit slightly) from its
orbit. The last I knew this just doesn't occur.
Also a muzzle brake would have no effect on reduction of recoil if the
rearward movement of the rifle upon discharge was mainly due to the
acceleration of the bullet and powder down the barrel, and not the
redirection of the escaping gas.
Jim Nasset
Aftermarket Innovations
http://www.inventorworld.com/ami
Jim Nasset
Jeffrey A. Del Col <br...@cleveland.Freenet.Edu> wrote in article
<5fca68$7...@xring.cs.umd.edu>...
#
(Snip)
# In a previous article, bev...@netcom.com (Bev Clark/Steve Gallacci)
says:
#By far the greatest proportion of recoil is generated
# by the bullet's acceleration. Fire a few blanks, and you'll see what
# I mean.
#
# J. Del Col
The reason that blanks do not have the same effect on recoil is because of
the fact that there is no resistance to the expanding gasses other than the
atmospheric pressure, the pressure build up in the barrel is nil. However
when a bullet is added to the case the gas pressure in the barrel is in the
order of 40,000 to 50,000 psi and when it (although reduced substantially
after the initial burn) escapes the barrel this is the cause of the recoil.
Steve Meyer
Bret Jensen wrote:
#
# COME ON. We all learned in high school physics that objects
# barrel there is no action to produce the "equal and opposite" reaction of
# recoil.
#
Are you suggesting that a bullet moving inside a barrel has neither
momentum nor energy? What we learned in high school physics was that
F=ma, force equals mass times acceleration. We also learned that for
every action there is an equal but opposite reaction. In the case of
a bullet travelling down a barrel, the force is supplied by the burning
powder, just as it is for the rest of the rifle! F is the same for
both! The masses are vastly different, and the accelerations will also
be vastly different, but that's physics. Recoil is composed of that
force _plus_ the jet effect force of the powder when the bullet leaves
the muzzle, but recoil starts the instant acceleration of the bullet
begins.
Recoil _does_ affect accuracy. With small forces, like a .22 rimfire,
and large firearm masses, like a target rifle, the effects are small.
With something like a .338 Mag in a 7 1/2 pound rifle, or any handgun,
the effects are large, and how a person grips the firearm is a definite
contributor to point of impact and group size. This is more true of
handgun than rifle, but very real for both. Try some shooting and see
for yourself!
Steve Meyer
Daniel E. Platt
In article <5f785g$o...@xring.cs.umd.edu>, sfa...@ihgp9.ih.lucent.com (-Faber,S.R.) writes:
|> In article <5f5mal$l...@xring.cs.umd.edu>,
|> ## the powder behind three to four times the bullet weight in the hands of
|> ## someone who isn't exactly holding the rifle the same for each shot and
|> ## it's a different story. When free recoil energy goes from 3 pounds to 30
|> ## pounds, there's going to be a lot more rifle movement before the bullet
|> ## exits the muzzle.
|> # COME ON. We all learned in high school physics that objects
|> #barrel there is no action to produce the "equal and opposite" reaction of
|> #recoil.
|>
|> You would expect the center of mass to stay at the same place as long
|> as the bullet is in the barrel. The center of mass at the start
|> is a little different than when the bullet is near the muzzle, so there
|> will be a little bit of recoil before the bullet exits, and it will be
|> greater with a lighter gun. It will be a pretty small effect though
|> since the change in center of mass is small, so your conclusion may
|> still be true.
|>
|>
In estimating amount of effect due to flinching, its best to start
by looking at what's happening to the rifle while the bullet is
in the barrel (using a simple constant-force calculation as appropriate
for back-of-envelope kinds of calculations, and not inconsistent with
the effect of a progressive burning powder).
Actually, the bullet gets almost all of its acceleration while the bullet
is in the barrel, so most of the energy released by the powder charge is
already expressed in momentum transferred to the rifle and bullet by the
time the bullet reaches the muzzle. The effect of a muzzle brake is to
re-absorb some of the rifle's momentum before it has moved very far back
into the shooter's shoulder. On the other hand, for a 200 gr bullet that
is accelerating in a 2 ft space (24'' barrel) to 2700 ft/sec, you'd expect
the time spent to be of the order of 0.0015 sec (using a back-of-envelope
constant force kind of calculation). The force on the rifle is large,
but it only lasts a tiny fraction of a second. Since the center of mass
remains pretty much constant while the bullet is in the barrel, the total
distance the rifle has moved while the bullet is in the barrel is of the
order of m x / M (m = bullet mass -- about 200 gr for arguments sake; M =
mass of rifle, about 8 lb [Ok.. divide all by g to get slugs, and gr/7000
= lb], length of barrel is x = 24''), to yield a backwards travel of about
0.086'' in the time the bullet is in the barrel. The rifle just hasn't
moved far enough for the shooter to have experienced much recoil while the
bullet is in the barrel -- but all of the momentum has been transferred.
If all of that had been perpendicular to travel, rather than backwards,
the total deflection would have been about 12.3 MOA. Regardless of how
the barrel rides above the center of gravity of the rifle, producing the
kind of torque that can produce deflection, the amount of deflection is
the same each shot, and just gets factored into the sight adjustment.
The average force on the rifle (and bullet) while the bullet was in the
barrel would have been about 135 lb. The final velocity of the rifle is
about 9.6 ft/sec, for a momentum of about 2.40 lb-secs (same for both
rifle and bullet).
Putting bounds on how much effect is produced by flinching is harder.
There are three components at the time the bullet is fired down the
barrel: 1) initial displacement, 2) initial velocity, and 3) force due
to flinch. Of these, the effect of initial displacement and initial
velocity due to flinching are totally determined before the bullet starts
its travel. The remaining two affect travel in the barrel. First, to get
a deflection of 1 MOA while the bullet is in the barrel, the acceleration
would have to be 530 ft/sec^2, and the applied flinch force would have
to be 131.7 lbs (nearly the size of the recoil force since the force
has to move the entire rifle 1 moa). To get 1 moa deflection in the
barrel travel time, the barrel only has to be moving 0.39 ft / sec.
This is about 4.7 in / sec. Most flinches don't take anything like a
second, and 4.7 in / sec would look like a fast lead for shooting at a
running target. This is within a realm where you'd just have to measure
it by experiment. However, the alignment precision for a 24'' barrel
to within 1 moa is 0.007'' (micrometer on a sandbag). At 4.7 in / sec,
it would only take .0015 secs to get the 1 moa displacement. In other
words, if you anticipated the shot for anything more than .0015 secs
(note: reaction time of fingers is about .1 secs), you'd be much more
likely to have produced a pre-shot displacement of 1moa than you would
have produced it from the flinch-induced initial velocity of the barrel
during the bullet-in-barrel travel time.
Dan
--
-------------------------------------------------------------------------------
Daniel E. Platt pl...@watson.ibm.com
The views expressed here do not necessarily reflect those of my employer.
-------------------------------------------------------------------------------
Michael Courtney
Jim Nasset (a...@inventorworld.com) wrote:
: Steve Spoldi <spo...@worldnet.att.net> wrote in article
: <5fcpsl$8...@xring.cs.umd.edu>...
: # Gentlemen,
: # I believe simple conservation of momentum can be applied, i.e. bullet
: # mass * bullet velocity = firearm mass * recoil velocity. This also
: # applies to the position displacement, bullet mass * barrel length =
: # firearm mass * change in position (while the bullet is in the barrel).
: # The same gas pressure that pushes the bullet down the barrel pushes the
: # firearm backwards. Does anyone agree?
: #
: # Sincerely, Steve S.
: Yes, the gas pressure reacts against the rifle when it is released at the
: muzzle.
: The often quoted statement is "for each action there is an equal and
: opposite reaction" which of course is true. The one not mentioned here is
: "a body at rest tends to remain at rest" which when both of these are
: applied using the formula F=MA you will quickly understand why, until the
: escaping gas leaves the muzzle, that there is insignificant reward motion
: of the rifle.
The law of conservation of momentum applies at every instant of time.
If the bullet has 2800 fps velocity just before it leaves the barrel,
then it has a momentum of 67.2 ft-lbs. The rifle must have an equal
and opposite momentum at that instant which requires an 8 lb rifle to
be moving rearward at 8.4 fps just before the bullet leaves the barrel.
As a result, the rifle will have moved 0.05 to 0.07 inches by the time
the bullet exits the barrel for a 30-06 or 308 and about three times
as much for a big game magnum such as a .416 Rigby.
: So what we have is 0.02407 foot pounds attempting to move an "at rest mass"
: of 10.5 pounds, sorry, but it is not going to happen. This also does not
: take into account the friction of the bearing surface of the bullet
: attempting to pull the rifle forward, or the friction between the stock and
: the sandbag, or the resistance of the mass of the upper body of a man,
: restricting the reward movement.
Your force analysis is deeply flawed. The momentum argument I give is
easier to understand, but if you must resort to a force-based calculation,
then the instantaneous rearward force on the rifle is
(pi*pressure*bullet diameter/4) - (force applied by bullet on rifling).
You appeal to the rifling's frictional force as a mitigating factor,
but it only reduces recoil to the same degree it reduces bullet
velocity because the forward force on the bullet is exactly the
same as the rearward force on the rifle. Ignoring the frictional effect
of the rifling only produces a small error in computing bullet velocities,
so I'll assume the error is also small when considering the rearward force
of the rifle. Suppose a modest peak pressure of 30,000 PSI in the
chamber. The rearward force on the rifle is
3.141 * 30,000 * (0.308)*(0.308)/4 = 2234 lbs.
: A simple test you can perform to duplicate the reaction of your rifle to
: this applied force, is to take a "very sensitive" pull gage, attach it to
: the butt, or trigger guard of your rifle while it is laying on a sand bag
: and apply 0.024077 pounds of pull to it and measure the distance the rifle
: moved. (Not much, was it.)
But use the correct force of 2234 lbs and see if it moves much. This large
force is only applied for about 1 milisecond, but it is applied when the
chamber pressure is at its peak. This is usually during the first 10 inches
or so of the bullet's travel down the barrel.
: If it were not true that the force needed to overcome an at rest mass must
: be more than the mass itself, every time a volcano erupted on earth, or a
: rocket was launched, the earth would be moved (albeit slightly) from its
: orbit. The last I knew this just doesn't occur.
Hogwash, but this is not the place to explain why.
: Also a muzzle brake would have no effect on reduction of recoil if the
: rearward movement of the rifle upon discharge was mainly due to the
: acceleration of the bullet and powder down the barrel, and not the
: redirection of the escaping gas.
Wrong again. After the rifle has fully accelerated backwards, the muzzle
brake deccelerates the rifle by diverting the gasses backward. In other words,
the rifle begins moving full speed toward the shoulder but only progresses
0.05" before the muzzle brake has its effect and slows the rearward progress.
: Jim Nasset
: Aftermarket Innovations
: http://www.inventorworld.com/ami
Do you mean that, as ignorant as you are about the basic physical
considerations of a bullet leaving a barrel, you are in the ballistics
business? If you don't understand conservation of momentum, how
can you possibly understand the complex harmonic vibration characteristics
on which your accurizer is supposedly based? In fact, you're probably
more lucky than smart, because just as it's easier to damp a guitar
string than play it's harmonics, it's easier to damp a rifle barrel
than play it's harmonics.
In any case, take my marketing advice and stop showing how little you know.
--
Michael Courtney, Ph. D.
mic...@amo.mit.edu
Steve Spoldi
Jim Nasset <a...@inventorworld.com> wrote:
#
#
#Steve Spoldi <spo...@worldnet.att.net> wrote in article
#<5fcpsl$8...@xring.cs.umd.edu>...
## Gentlemen,
## I believe simple conservation of momentum can be applied, i.e. bullet
## mass * bullet velocity = firearm mass * recoil velocity. This also
## applies to the position displacement, bullet mass * barrel length =
## firearm mass * change in position (while the bullet is in the barrel).
## The same gas pressure that pushes the bullet down the barrel pushes the
## firearm backwards. Does anyone agree?
##
## Sincerely, Steve S.
#
#Yes, the gas pressure reacts against the rifle when it is released at the
#muzzle.
#
#The often quoted statement is "for each action there is an equal and
#opposite reaction" which of course is true. The one not mentioned here is
#"a body at rest tends to remain at rest" which when both of these are
#applied using the formula F=MA you will quickly understand why, until the
#escaping gas leaves the muzzle, that there is insignificant reward motion
#of the rifle.
#
#The mass of a 168 grain bullet combined with the mass of 45 grains of
#powder is 0.0009461. The velocity of the bullet from a 26 inch barrel is
#2650 fps. And the weight of my .308 Rem VS including scope is 10.5 pounds
#and its mass is 0.3264925.
#
#The force acting against the rifle caused by the acceleration of the bullet
#and powder down the barrel can then be calculated using the above
#parameters.
#
#Force = 0.0009461 times 2650 fps times .01 seconds (the time it takes the
#bullet to traverse the barrel)
#Force = 2.507165 pounds times .01 sec
#Force = 0.02507 foot pounds.
#
#So what we have is 0.02407 foot pounds attempting to move an "at rest mass"
#of 10.5 pounds, sorry, but it is not going to happen. This also does not
#take into account the friction of the bearing surface of the bullet
#attempting to pull the rifle forward, or the friction between the stock and
#the sandbag, or the resistance of the mass of the upper body of a man,
#restricting the reward movement.
#
#A simple test you can perform to duplicate the reaction of your rifle to
#this applied force, is to take a "very sensitive" pull gage, attach it to
#the butt, or trigger guard of your rifle while it is laying on a sand bag
#and apply 0.024077 pounds of pull to it and measure the distance the rifle
#moved. (Not much, was it.)
#
#If it were not true that the force needed to overcome an at rest mass must
#be more than the mass itself, every time a volcano erupted on earth, or a
#rocket was launched, the earth would be moved (albeit slightly) from its
#orbit. The last I knew this just doesn't occur.
#
#Also a muzzle brake would have no effect on reduction of recoil if the
#rearward movement of the rifle upon discharge was mainly due to the
#acceleration of the bullet and powder down the barrel, and not the
#redirection of the escaping gas.
#
#Jim Nasset
#Aftermarket Innovations
#http://www.inventorworld.com/ami
#
#
Jim,
I think you have an error in your calculation. If I use your values for mass,
bullet speed, and barrel length, I compute the following parameters:
rifle recoil speed = 8 feet/second
rifle recoil energy = 10 foot*pounds
bullet transit time in barrel = 0.0016 seconds
I hope this helps, I'm sorry I don't have time to elaboate just now.
Sincerely, Steve Spoldi
Dale Stanton
On 3/1/97 8:02PM, in message <5fajj2$3...@xring.cs.umd.edu>, Larry Bump
<lb...@mail.bright.net> wrote:
# #Bret Jensen <bje...@willamette.edu> wrote in article
#
# ## COME ON. We all learned in high school physics that objects
# ## maintain their momentum unless acted upon. Until the bullet leaves the
# ## barrel there is no action to produce the "equal and opposite" reaction of
# ## recoil.
With all due respect, that is silly. That's not what I learned.
# the bullet wedged in the barrel. There WAS a noticeable recoil impulse,
# though obviously not very much.
Not much "felt" recoil, because the accelleration was immediately counter-acted
by the deceleration after the powder had done its job. It started at zero,
accellerated to "n" fps, then decelerated back to zero...all within the barrel.
Methinks thou art confused.
--
Internet: da...@zoomnet.net
*** Do NOT send advertisements to my Email address. ***
*** http://www.zoomnet.net/~dalet/index.html ***
Michael Courtney
Jim Nasset (a...@inventorworld.com) wrote:
: COME ON. We all learned in high school physics that objects
: maintain their momentum unless acted upon. Until the bullet leaves the
: barrel there is no action to produce the "equal and opposite" reaction of
: Jim Nasset
: Aftermarket Innovations
It has occurred to me that Mr. Nasset may have a selfish reason for spouting
such pseudo-science as fact. After if recoil-induced "muzzle flip" is capable
of intruducing inaccuracy in certain rifles, then the "accurizer" which
he sells is not a silver bullet or cure all for accuracy. Regardless of
what the physics says, Mr. Nasset has a large financial interest in recoil
not influencing accuracy.
The facts are:
Physics says a 30-06 or .308 moves 0.05 to 0.07" before bullet leaves
the barrel.
Nasset says rifles don't recoil until after the bullet has left the barrel.
Physics says force of recoil is several thousand pounds while the bullet is
in the barrel.
Nasset says force of recoil is a fraction of a pound while the bullet is in
the barrel.
The amount of muzzle-flip induced by recoil while the bullet is in the barrel
depends on several factors. 1) The momentum transfer (recoil) 2) The
perpendicular distance from the barrel line to the fulcrum 3) The moment
of inertia about the fulcrum. In certain holds, the rifle is essentially
free during the time the bullet is in the barrel and the fulcrum is provided
by the rifle's center of mass. This is because soft materials such as
flesh and clothing provide little resistance to the recoiling rifle's
motion of 0.05" or so during the millisecond that the bullet is in the barrel.
However a more strongly recoiling rifle such as a .416 Rigby will meet stronger
resistance from the flesh because it moves three or four times as far during
the millisecond that the bullet is in the barrel.
Craig Hull
On 27 Feb 1997 23:18:29 -0500, Bret Jensen <bje...@willamette.edu>
wrote:
# COME ON. We all learned in high school physics that objects
#maintain their momentum unless acted upon. Until the bullet leaves the
#barrel there is no action to produce the "equal and opposite" reaction of
#recoil.
# I saw a series of high-speed strobe photos taken by Winchester in
#the 50s in which they had the muzzle of a Model 94 resting on a black
#block and a white sheet behind the rifle. With the bullet 1/2" out of
#the muzzle, there was no white space yet visible between the muzzle and
#block. With the bullet about 1 1/2 inch out of the muzzle, there was a
#thin white line visible between muzzle and block. The pictures were
#captioned, "Why felt recoil does not influence bullet strike," or
#something close to that.
There is a distinct difference between the statement in the first
paragraph and the caption quoted in the second. As has competently
explained in a number of responses so far, the recoil action of the rifle
starts at the same moment that the bullet starts moving. However, the
caption refers to 'felt recoil'. Others have quoted calculation giving
the movement of the rifle during the time the bullet is traversing the
barrel. All of these that I read so far give a movement of less than
1/10th inch. This will be enough to affect point of impact but likely is
not enough to be felt. What is felt will be the continued movement (but
not acceleration) of the rifle.
Without having the picture and caption in context I have no idea how the
original author developed his (her?) idea. If they claims that recoil
does not affect point of impact it's BS. But if they were in fact
distinguishing between recoil and 'felt recoil' one would have to see how
they define and use the terms.
--
Craig
Arrogance seeks to knows all the answers,
Wisdom seeks to understand the questions.
Jeffrey A. Del Col
In a previous article, kei...@bctv.com (Keith Wood) says:
#In article <5fc5vr$6...@xring.cs.umd.edu>,
#br...@cleveland.Freenet.Edu (Jeffrey A. Del Col) wrote:
#[
#[In a previous article, a...@inventorworld.com (Jim Nasset) says:
#[
#[#Boy, you have opened a can of worms now. About a year ago I attempted to
#[#explain to a number of "disbelievers" in the group that any (rearward)
#[#rifle movement from recoil prior to the exit of the bullet from the muzzle
#[#was insignificant. This is simply because the mass of the bullet and powder
#[#moving down the barrel is insufficient to overcome the many times greater
#[#at rest mass of the rifle.
#[
#[
#[
#[Are you saying that the bullet/ propellant mass-- increases-- when
#[the bullet leaves the barrel? That's nonsense.
#
#[It may take a bit longer for the mass of the shooter to get moving, but
#[that's another problem. The recoil force has to peak before the
#[bullet leaves the barrel.
#
#No. You are assuming that recoil is solely from the mass/veslocity
#of the bullet, which ignoes the GREATEST component of recoil:
#
#THRUST.
#
More nonsense. The thrust in a rocket engine is produced --inside--
the engine. The exhaust plume outside the nozzle contributes exactly
nothing to thrust. In fact it decreases the performance
of the rocket by becoming subject to atmospheric
drag. The same is true of muzzle blast. The propellant gases
--must-- interact with the walls of the bore in order to produce
thrust. Once the gases exit the bore, they expand, cool off
and --slow down--. They have already contributed their maximum thrust
before they leave the bore.
Once the gases leave the bore, they cannot suddenly produce more thrust.
They expand against the air, not the bore, cool off and slow down.
The --only-- way the propellant mass could contribute a greater proportion
to recoil than the mass of the bullet would be if the
propellant mass exceeded the mass of the bullet (which is only the
case in some experimental cartridges employing huge
powder charges with very light bullets) or if the propellant
was by some miraculous property accelerating much faster than the
bullet--- in front of it--. Think about it a minute.
F=MA is it as far as recoil production is concerned, unless you've come up
with some way around old Isaac's laws.
Jeffrey A. Del Col
#When you fire a rifle, the bullet is propelled by an expanding mass
#of propellant gasses. Once the bullet leave the muzzle, those gasses
#are released to the outside. They then provide thurst in the same
#manner as a rocket engine, and in fact a solid-fuel rocket is nothing
#more than a cartridge with no projectile.
#
#[If a rifle were fired in free fall in a vacuum, the immediate acceleration
#[due to recoil would be obvious.
#
#
#There are two components to the thrust from the muzzle, mass-reaction
#(the movement of mass, including the expanding propellant gasses] and
#aerodynamic pressure (as the expanding could of gas pushes against
#the outside air while still at a high pressure in the bore).
Then I guess rockets don't work in a vacuum?
Think about this a second
The --only-- source of any significant thrust in a rifle
or a rocket is the interaction between the accelerating mass
of the propellant and projectile with the walls
of the rifle bore or combustion chamber.
The presence of air imposes a drag penalty on the exapansion of the gases in
a rocket that vastly outdoes any alleged thrust benefit.
Rocket engine designers understand this all too well;
that's why exhaust nozzles for rockets used in space have to be
shaped differently to allow for the much more rapid and efficient
expansion of the exhaust gases in the vacuum of space
A bullet moving down a bore is also subject to aerodynamic
drag, particularly when
it goes supersonic. All the drag does is retard acceleration;
It can't possiblly increase it--therefore it cannot increase the
recoil.
The same applies to the propellant gases, comprende?
Sheeesh.
Dan Brown
Jim Nasset <a...@inventorworld.com> wrote:
# The often quoted statement is "for each action there is an equal and
# opposite reaction" which of course is true. The one not mentioned here is
# "a body at rest tends to remain at rest" which when both of these are
# applied using the formula F=MA you will quickly understand why, until the
# escaping gas leaves the muzzle, that there is insignificant reward motion
# of the rifle.
"A body at rest tends to remain at rest" until acted upon by
an outside force. Simple inertia. Since there _is_ an outside force
(the equal and opposite reaction), this argument is moot (and has
already been mentioned here).
You have not explained why the release of the gas at the
muzzle should cause such a significant rearward motion, though; this
is rather important in light of the rest of your argument. However,
some of your calculations are mistaken.
# The mass of a 168 grain bullet combined with the mass of 45 grains of
# powder is 0.0009461. The velocity of the bullet from a 26 inch barrel is
# 2650 fps. And the weight of my .308 Rem VS including scope is 10.5 pounds
# and its mass is 0.3264925.
I assume the units of mass you're using are slugs; it would be
well to name units here (and elsewhere). Numbers without units are
meaningless.
# The force acting against the rifle caused by the acceleration of the bullet
# and powder down the barrel can then be calculated using the above
# parameters.
Agreed, but...
# Force = 0.0009461 times 2650 fps times .01 seconds (the time it takes the
# bullet to traverse the barrel)
# Force = 2.507165 pounds times .01 sec
# Force = 0.02507 foot pounds.
This isn't the right way to do it. Force is mass x
*ACCELERATION*, not velocity. To derive acceleration, you divide the
change in velocity by the change in time, thus you'd do (2650 fps /
0.01 sec), yielding 265,000 ft/sec^2 as acceleration.
Second, your units don't work out. Because I'm more familiar
with the metric units in this context, I'll use them for this
explanation, rounding the numbers for the sake of simplicity.
Force = 15 g x 800 m/sec / 0.01 sec
= 0.015 kg x 80,000 m/sec^2
= 12,000 kgm/sec^2
= 12,000 Newtons
At normal gravitational conditions, newtons can be converted
to kgs with 9.8 N/kg, so that makes a force of about 2700 pounds.
Staying in metric units:
12,000N = 5 kg x acceleration
2400m/sec^2 = acceleration
Now, to determine how fast the rifle would be moving (without
any other interference, of course):
velocity = acceleration x time
= 2400 m/sec^2 x 0.01 sec
= 24 m/sec
= 79 ft/sec
Of course, this makes several assumptions (like that
acceleration is constant, which it probably isn't), and relies on no
outside influence on the rifle, which is never the case.
Note that most of the other correspondents on this thread have
suggested an in-barrel time of about 0.001 second, which would
increase most of these numbers by a factor of ten. I don't personally
know which is accurate, so I'm using your numbers.
# If it were not true that the force needed to overcome an at rest mass must
# be more than the mass itself, every time a volcano erupted on earth, or a
# rocket was launched, the earth would be moved (albeit slightly) from its
# orbit. The last I knew this just doesn't occur.
I believe that you're mistaken in this, although for the
reasons shown above it doesn't matter to this case. Even using the
numbers you came out with, though (0.025 lb force), you _still_ will
have the rifle accelating at 0.0715 ft/sec^2. F=MA doesn't
distinguish between cases where the F/M ratio is small and ones where
it's large; it applies to all cases. For a proof of this, place a 10
lb weight on an air table and apply a slight force to it--it will
move, though slowly.
One counterexample: in zero gravity (as aboard the space
shuttle), a 200lb person doesn't have to apply 200 lb of force to get
himself moving. Since there is no significant counter-force, a very
slight push will do fine.
Second counterexample (which I've posted here already, but
doesn't seem to have made it): If recoil is so insignificant until the
bullet leaves the barrel, why do many recoil-operated firearms need
locking breeches? See Glock, 1911, SIG, S&W, Beretta, etc--the barrel
and slide move together for a bit before they unlock, to keep the
action from opening while dangerous pressures are still present. But
if there were no significant recoil until the bullet had left the
barrel, there would be no great pressure left in the chamber, and thus
no reason to lock the action at all. On the same vein, why have
gas-operated firearms?
# Also a muzzle brake would have no effect on reduction of recoil if the
# rearward movement of the rifle upon discharge was mainly due to the
# acceleration of the bullet and powder down the barrel, and not the
# redirection of the escaping gas.
As far as I've seen, nobody's claiming that the escaping gas
doesn't have _a_ part in recoil--just that the bullet's acceleration
is also a part, and a substantial one at that. As you say, here's the
math, and the numbers look pretty substantial.
--
Dan Brown, KE6MKS, da...@value.net
Finger bro...@holmes.uchastings.edu for public key & Geek Code
E-Mail published at my discretion.
Doug L Ivers
# From: Michael Courtney <michael@amo>
big snip
#
# Wrong again. After the rifle has fully accelerated backwards, the muzzle
# brake deccelerates the rifle by diverting the gasses backward. In other
words,
# the rifle begins moving full speed toward the shoulder but only
progresses
# 0.05" before the muzzle brake has its effect and slows the rearward
progress.
#
Actually, most (but not all) muzzle brakes I have seen divert the gas at 90
degree angle, not back to the shooter. While they do not subtract from the
recoil caused by the bullet, they do prevent the mass and velocity of the
powder from being added. I have read that a velocity of 4200 ft/s should
be used when calculating the extra recoil caused by the powder. On magnum
rifle cartridges the mass and velocity of the powder account for a large
part of the recoil.
In my .338 Winchester (250 grain bullet at 2700 ft/s, 71 grains of powder)
the powder accounts for 31% of the total recoil. For magnum rifles that
shoot lighter bullets the percentage is even higher.
Doug
st...@grove.ufl.edu
#
# nothing to thrust. In fact it decreases the performance
# of the rocket by becoming subject to atmospheric
# drag.
The nozzle encourages the gas to cool and expand, increasing it's velocity
and providing more thrust. This is very simmilar to the expander in a
turbo charger. It is essentially a heat energy coversion device.
If the nozzle just contributed todrag, it would be rather silly having one,
wouldn't it?
Mike
Doug L Ivers
#
# The same is true of muzzle blast. The propellant gases
# --must-- interact with the walls of the bore in order to produce
# thrust. Once the gases exit the bore, they expand, cool off
# and --slow down--. They have already contributed their maximum thrust
# before they leave the bore.
#
The propellant pushing against the bolt of the rifle is what forces the gun
back, the major effect of the propellant on the bore is throat erosion.
#
# The --only-- way the propellant mass could contribute a greater
proportion
# to recoil than the mass of the bullet would be if . . .
#the propellant
# was by some miraculous property accelerating much faster than the
# bullet--- in front of it--. Think about it a minute.
#
That is exactly what happens. Only the propellant does not reach it's top
speed until after the bullet is free of the bore. If you see a picture of
a bullet right after it leaves the muzzle you will see a rapidly expanding
gas cloud overtaking the bullet.
Doug
Soren LaForce
In article <5fivmp$n...@xring.cs.umd.edu> Jeffrey A. Del Col,
br...@cleveland.Freenet.Edu writes:
#
# The --only-- way the propellant mass could contribute a greater
proportion
# propellant mass exceeded the mass of the bullet (which is only the
# case in some experimental cartridges employing huge
# powder charges with very light bullets) or if the propellant
# was by some miraculous property accelerating much faster than the
# bullet--- in front of it--. Think about it a minute.
#
Actually, the propellant can (and does) move faster than the bullet.
Once the bullet clears the barrel, the propellant is free(er) to
accelerate and will move faster than the bullet; if it weren't
able to expand that much, it would no longer be pushing the bullet
by the end of the barrel (I suppose that a *really wimpy* load
could be the exception).
No, I do not think that the propellant contributes more to the
recoil than does the bullet.
--Soren
-my opinions-
Mathew P. Lamita
#Dan Brown <da...@value.net> wrote in article
<5fl04n$r...@xring.cs.umd.edu>...
# Jim Nasset <a...@inventorworld.com> wrote:
Dan I enjoyed following your reasoning, but I'm really disappointed that
you didn't mention "Conservation of Momentum." It is really an easy
problem just using this conservation law.
The momentum of the system (bullet and rifle) must remain constant.
The bullet and rifle are stationary initially. The bullet is fired (moves
forward) and the rifle recoils (moves backward).
Now, to solve this for the velocity of the rifle we use the following
equation:
p = p where p = mass x velocity
- (mass of bullet) x (velocity of bullet) / (mass of rifle) = (velocity of
rifle)
the key for this is to remember to use the correct units. Choose a system
and stay with it. You are going to need a mass and a velocity. You can't
mix grains and pounds and have a correct answer. Make the conversions and
enjoy.
Mathew P. Lamita
Mark L. Mitchell
In article <5fc654$6...@xring.cs.umd.edu>, da...@value.net (Dan Brown) wrote:
#andy...@aol.com (Andykun66) wrote:
#
## fps. less muzzle velocity, they hit 2 inches higher. What this is telling
## me is the gun is recoiling while the bullet is still in the barrel. Is
## this a reasonable conclusion?
#
# IMHO, that isn't a reasonable conclusion, because the data
#you've given support another conclusion just as strongly (if not more
#so)--trajectory varies with velocity, after all.
I witnessed this with some of my pistols. I have a S&W 1006 that shot really
low. I tried cranking up the loads but the problem only got worse. My
brother, an armorer and instructor, told me to try reducing my loads. Sure
enough, light loads shot higher. The oposite of what I first thought. This
would leave me to conclude that the weapon is recoiling while the bullet is
still in the barrel because the longer is spends there the further it rose.
Actually, thinking about it, I would be hard to beleive that the recoil
wouldn't start the moment the bullet started moving.
I have also heard or read that a major portion of recoil is a result of the
gasses leaving the barrel.
st...@grove.ufl.edu
# >The nozzle encourages the gas to cool and expand, increasing it's
# velocity
# >and providing more thrust. This is very simmilar to the expander in a
# >turbo charger. It is essentially a heat energy coversion device.
#
# As a gas expands and cools, its velocity DECREASES. That is the
# principle behind mufflers and suppressors on firearms. The nozzle
# serve to keep the exhausting gasses moving in a desired direction.
I stand by my origional statement. I wish, however to point out two
things:
1. My complete statement which you did not quote was in referance to the
nozzles on rocket engines.
2. Outside of the barrel pressure is fixed at 1 atm. As volume goes up,
velocity must also go up as the gas takes up more space and velocity is
distance over time.
3. You will find reference to the additional "push" the muzzle blast gives
the bullet in a number of gun publications. You can also read just about
any technical paper on turbo chargers, or expanders in airconditioners and
heat pumps, and jet engines Also, if you have a chemistry or termodynamic
text book, you can look up "adiabatic expansion".
4. I am a physict, I am paid to know these things :-)
Mike
Mathew P. Lamita
Mark Yaworski
#The nozzle encourages the gas to cool and expand, increasing it's velocity
#and providing more thrust. This is very simmilar to the expander in a
#turbo charger. It is essentially a heat energy coversion device.
As a gas expands and cools, its velocity DECREASES. That is the
principle behind mufflers and suppressors on firearms. The nozzle
Dan Brown
"Mathew P. Lamita" <mla...@umd.umich.edu> wrote:
# Dan I enjoyed following your reasoning, but I'm really disappointed that
# you didn't mention "Conservation of Momentum." It is really an easy
# problem just using this conservation law.
That would have been another way to approach the problem, all
right. I was just trying to stay within the framework of what was
originally posted, even though the force-based analysis ends up being
a bit more complicated...