Lighter bullets shoot lower???
pert...@netcom.com
even though the lighter bullets are faster. I do not understand why this
might be so. I hear this about handguns, if it makes any difference. Can
someone offer some insight into the physics or geometry of guns/sight
alignment that can explain this?
Thanks.
Daniel Morris DeRight
pert...@netcom.com writes:
#
# I repeatedly hear that lighter bullets shoot lower than heavier
# bullets, even though the lighter bullets are faster. I do not
# understand why this might be so. I hear this about handguns, if it
# makes any difference. Can someone offer some insight into the
# physics or geometry of guns/sight alignment that can explain this?
Well, from my experience, you've heard right. The reason is
fairly simple, when you stop thinking about what the bullet does out
of the gun, and concentrate on what it does in the gun. The faster
bullet will shoot lower for two reasons. First, lighter bullets often
have less momentum, and therefore less felt recoil, which means the
gun will react differently when it is fired. Secondly, and more
importantly, the heavier bullets are going slower, so they spend more
time in the barrel. That barrel is rising from the time they are
fired, so the heavier bullets exit at a higher angle than the lighter
ones, giving them a higher impact point as well.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
soda...@cmu.edu sdesigns
NRA Life & proud Humidors & Woodcraft
Never forget those who 4902 Forbes Avenue, Box 235
died, that we might Pittsburgh, PA 15213
live as we do. -TJ 412-441-5036
The law should be stable, but should never stand still. -O.W.H.
Alexander I
: I repeatedly hear that lighter bullets shoot lower than heavier bullets,
: even though the lighter bullets are faster. I do not understand why this
: might be so. I hear this about handguns, if it makes any difference. Can
: someone offer some insight into the physics or geometry of guns/sight
: alignment that can explain this?
Well, I'm not an expert on this sort of thing, and you have left a number
of variables in the equation. However, if I were you, I would think about
the effects of recoil on the shooter from a heavy load with heavy bullets
versus something lighter.
--
Eric J. Obermeyer (ejob...@mtu.edu) **** "And now that the
legislators and do-gooders have so futilely inflicted so many systems
upon society, may they finally end where they should have begun: May
they reject all systems, and try liberty..." -- Frederic Bastiat, 1850
Bob Catherwood
# I repeatedly hear that lighter bullets shoot lower than heavier bullets,
# even though the lighter bullets are faster. I do not understand why this
# might be so. I hear this about handguns, if it makes any difference. Can
# someone offer some insight into the physics or geometry of guns/sight
# alignment that can explain this?
#
# Thanks.
I'm told that because heavier bullets are slower, they remain in the
barrel longer. Therefore, recoil has more time to act, lifting the barrel
and the point of impact.
Rick Enriquez
# I repeatedly hear that lighter bullets shoot lower than heavier bullets,
# even though the lighter bullets are faster. I do not understand why this
# might be so. I hear this about handguns, if it makes any difference. Can
# someone offer some insight into the physics or geometry of guns/sight
# alignment that can explain this?
#
# Thanks.
I found this to be true in my .44 magnum handguns. I suppose the reason
for this is that the heavier bullets tend to have higher recoil and lower
velocity. Therefore, the bullet leaves the barrel from a higher angle.
--
_________________________________________________________________
Rick Enriquez rick_e...@bio-rad.com
Torsten Hoff
#even though the lighter bullets are faster. I do not understand why this
#might be so. I hear this about handguns, if it makes any difference. Can
#someone offer some insight into the physics or geometry of guns/sight
#alignment that can explain this?
#
#Thanks.
#
It's not the bullet weight per se that makes the difference. The problem is
that the lighter bullets are usually loaded to higher velocities, which pushes
them out the barrel faster, which in turn gives the barrel less time to rise
from the recoil. Since the barrel will point lower (than for a standard
velocity round) at the time the bullet exits, the bullet will impact lower.
Torsten Hoff
th...@symantec.com
(The views and opinions expressed here are my own,
and should not be construed as representing those
of Symantec Corp.)
bogie
#even though the lighter bullets are faster. I do not understand why this
#might be so. I hear this about handguns, if it makes any difference. Can
#someone offer some insight into the physics or geometry of guns/sight
#alignment that can explain this?
I commonly shoot wimp .38 special loads, with 148 to 158 grain cast bullets out of a .357. When
I load up 125 grain JHP .357 magnum loads, I find myself grouping several inches LOWER.
One theory advanced was that the bullet was exiting the barrel faster, and there was less of a
"recoil" effect on it... This seemed weird...
Soren LaForce
#I repeatedly hear that lighter bullets shoot lower than heavier bullets,
#even though the lighter bullets are faster. I do not understand why this
#might be so. I hear this about handguns, if it makes any difference.
Can
#someone offer some insight into the physics or geometry of guns/sight
#alignment that can explain this?
The faster bullet leaves the barrel sooner.
If the barrel pitches up (from recoil), then the heavier
bullet exits at a higher inclined angle from horizontal as
the barrel has had more time to rise.
I've noticed this effect primarilly with my enfield while
shooting sks (123gn) bullets. I experienced a drop of several
inches at only 50 yards. Grouping was similar with either
load (123 or 180 gn), just several inched lower with the
lighter bullets.
I haven't chrono'ed either load yet (didn't have the crono
then) and I don't remember the expected (loading data)
velocities.
--Soren
soren_...@qmgate.arc.nasa.gov
DEADIN
flatter trajectories. The flatter trajectory will cause the bullet to
reach the target before it rises as high as a slower bullet with a greater
mid range trajectory. This is assuming the same sight setting for both
bullets. The higher velocity also causes the bullet to have less "barrel
time" and therefor have less time to be effected by the recoil. (The
recoil starts the instant the bullet begins to move.) This is more
noticable in pistols than in rifles. A good example would be to compare
the front sight height on an eight inch .357 against a two inch.
Dean in Seattle
Keith Kushner
: I repeatedly hear that lighter bullets shoot lower than heavier bullets,
: even though the lighter bullets are faster. I do not understand why this
: might be so. I hear this about handguns, if it makes any difference. Can
: someone offer some insight into the physics or geometry of guns/sight
: alignment that can explain this?
Seems a bit counter-intuitive, doesn't it? The slower bullet remains in the
barrel longer, so the barrel will have recoiled further upward before the
bullet clears it.
--
* Keith Kushner * Quis custodiet ipsos custodes? - Juvenal *
* myc...@dorsai.dorsai.org * *
Rosco Benson
#==========pert...@netcom.com, 9/21/95==========
#
#I repeatedly hear that lighter bullets shoot lower than heavier bullets,
#even though the lighter bullets are faster. I do not understand why this
#might be so. I hear this about handguns, if it makes any difference. Can
#someone offer some insight into the physics or geometry of guns/sight
#alignment that can explain this?
This phenom...phenom...phenom..SITUATION is caused by the fact
that the light bullets are, typically, travelling FASTER. The amount
of time they spend in the barrel is SHORTER, so they are less
effected by the UPWARD thrust of recoil. That is to say, they exit
the bore SOONER in the upward recoil cycle...thus they hit lower.
This is extemely evident in guns that recoil significantly...like an
alloy-framed snubbie...and these particular guns seldom have
adjustable sights with which one might correct for this. The snubbies
with barrel-porting...like Jack Weigand is turning out...have to
be equipped with very short front sights to allow for this. The
Hybrid-comped autos also require a short front sight and/or a
tall rear one.
Rosco S. Benson
AT&T GIS Data Services
My opinions...not my employer's
"Whoever said life is fair"
motto of the Paladin Program
(invoked in cases of snivelling)
Louis J Boyd
#I repeatedly hear that lighter bullets shoot lower than heavier bullets,
#even though the lighter bullets are faster. I do not understand why this
#might be so. I hear this about handguns, if it makes any difference. Can
#someone offer some insight into the physics or geometry of guns/sight
#alignment that can explain this?
I'll try a simple explanation. When a gun fires the force on the bullet and
the chamber are (approximately) equal and of opposite direction while the
bullet is in the barrel. The direction a bullet travels is close to the
direction the barrel is pointed at the instant it leaves the barrel. As the
gun recoils, it not only accelerates rearward, but also picks up a rotational
acceleration around the center of gravity. On almost all pistols and rifles
the center of gravity is below the centerline of the barrel, so the barrel
rotates upward as the bullet travels down the barrel. Consider a light and
heavy bullet which leave the barrel at the same velocity. The force required
to
accelerate the heavier bullet is greater, so the forces on the gun must also
be greater, and in the time the bullet is in the barrel, the gun with the
heavier bullet will rotate further. More typically, lighter bullets leave the
barrel faster with the forces on the gun being more nearly equal. In this case
the gun accelerates a more nearly equal rate with the two bullets but the
lighter bullet gets out of the gun sooner when the gun hasn't rotated as far.
It's interesting that the amount of rotation before bullet exit is almost
independent of velocity and only a function of bullet weight for a given gun.
There is a slight effect of the additional mass of the powder charge as loads
are increased, but the effect is slight.
Since this effect is fixed for a given bullet weight, it doesn't affect
accuracy
as long a one doesn't mix bullet weights. It does cause a real problem for
guns with fixed sights.
Of course, at ranges where the effect of bullet drop as a function of velocity
and drag become controling, the bullet trajectories may cross. They may even
cross twice. Most ballistics programs don't take muzzle rise into account as
they assume you have zeroed the gun for a given bullet.
ZCarter530
Center of mass is the relevant concept. The amount of time the
bullet
spends in the barrell has nothing to do with it. The weight of the bullet
*is*
what makes the difference.
Steve Catt
Marco copy of the Colt SAA. The heavier bullets - e.g. 255 grains -
shoot considerably higher than 200 gr bullets. These (200 gr) shoot
c.2" above point of aim at 20 yards while the 255 gr are about 6"
high. This is explained by the fact that the gun begins to recoil
as soon as the cartridge is fired i.e. before the bullet leaves the
barrel. So the bullet exits the barrel as it is moving upwards in
recoil. A heavy bullet will generate more recoil than a light one
therefore it will exit the muzzle higher up the recoil arc.
I think it is a factor of both bullet weight and velocity, with
bullet weight being the most significant influence. So if you drove a
heavier bullet at the same velocity as a light bullet, it would
still shoot higher because of the greater recoil effect of the heavy
bullet. But that raises the question as to whether, if you download
a heavy bullet sufficiently, you can get it to shoot to the same
point of aim as a light one.
I don't have the physics to answer that last point or to explain
the whole phenomenon. Perhaps a 'rec.gunner' who is more familiar
with Newtonian physics can explain it. Is it to do with his Third
Law that every action has an equal and opposite reaction?
Steve
#I repeatedly hear that lighter bullets shoot lower than heavier bullets,
#even though the lighter bullets are faster. I do not understand why this
#might be so. I hear this about handguns, if it makes any difference. Can
#someone offer some insight into the physics or geometry of guns/sight
#alignment that can explain this?
#
#Thanks.
#
#
#
#
pert...@netcom.com
the correct one, namely that heavier bullets are in the barrel longer thus
allowing more time for the muzzle to lift before they exit. This is still
somewhat troubling to me, because it would imply that the same gun with the
same bullets might shoot substantially higher or lower for different people.
This may indeed be the case, but it's not something that I've noticed. Of
course, this effect will become more pronounced at longer ranges, and maybe
I haven't enough experience beyond 50 feet. Thanks again.
pertinax
ZCarter530
#Thanks to everyone that replied. It sounds like the obvious explanation
is
#the correct one, namely that heavier bullets are in the barrel longer
thus
#allowing more time for the muzzle to lift before they exit.
Nope.
For example, take a 180 grain 30-06 bullet fired from an 8 pound
rifle
with a 24 inch barrell. Question, how far does the rifle recoil during
the time
the bullet is in the barrell?
Making use of the concept of center of mass, the bullet moves
forward 24
inches. The rifle weighs 56,000 grains. So, the rifle moves back 24 * (
180 / 56000 )
or 0.077 inches. Notice that the time which the bullet spends in the
barrell doesn't
appear anywhere.
The barrell will also tip up slightly since the barrell lies
slightly above the center of
mass of the barrell, but the same point applies. The time which the
bullet spends
in the barrell is completely irrelevant. It is the *weight* of the bullet
that matters.
Assuming the bullet above has a muzzle energy of 2700 ft-lb, the
average
rearward force on the rifle while the bullet is in the barrel is 1350
pounds. In
comparison, the force you exert holding the rifle is small. Thus the
rather minor
effect of the tightness of hold on bullet placement.
DAVID JOHNSON
Lighter bullets in a handgun travel faster and produce less recoil
and less barrel rise prior to exiting the barrel therefore they
generally will print lower at normal handgun ranges.
--
Jim Lentz Bldg A 8343
bogie <bo...@vulcan.inlink.com> wrote:
##I repeatedly hear that lighter bullets shoot lower than heavier bullets,
##even though the lighter bullets are faster. I do not understand why this
##might be so. I hear this about handguns, if it makes any difference. Can
##someone offer some insight into the physics or geometry of guns/sight
##alignment that can explain this?
#
#I commonly shoot wimp .38 special loads, with 148 to 158 grain cast bullets out of a .357. When
#I load up 125 grain JHP .357 magnum loads, I find myself grouping several inches LOWER.
#One theory advanced was that the bullet was exiting the barrel faster, and there was less of a
#"recoil" effect on it... This seemed weird...
I can back this up. I have fired a .38 special, .357 magnum
and .357 maximum from my .357 maximum barrel on my T/C
Contender. The faster rounds hit lower than the slower
rounds in the case of all 3 cartridges.
Jim
--
Jim Lentz Work ---> (le...@tellabs.com) Home ---> (le...@mcs.com)
These opinions are mine (maybe) and not those of my employer.
Jim Lentz Bldg A 8343
ZCarter530 <zcart...@aol.com> wrote:
#
# Center of mass is the relevant concept. The amount of time the
#bullet
#spends in the barrell has nothing to do with it. The weight of the bullet
#*is*
#what makes the difference.
#
Can't agree with this. Firing the same weight projectile in
.357 magnum and .357 maximum from the same barrel resulted
in the maximum hitting lower because the round left barrel
quicker than the magnum.
Gil Broydes
tumble. As a result their trajectory dips down.
Only free men have guns.-Thomas Jefferson
Gil Broydes
Brian Morgan
My assumption would be that they would both (slow and fast bullet)
drop at the same speed (that gravity thing, Galileo, and all that),
but the faster bullet would be farther from you as it drops. As a
slow and fast bullet pass the target range, the slow bullet would
have dropped further, because it took longer to get there.
Just my logic...
Brian
Bruce Langdon
#Thanks to everyone that replied. It sounds like the obvious explanation is
#the correct one, namely that heavier bullets are in the barrel longer thus
Hatcher's Notebook, pages 290-298, has sections titled
Recoil before the bullet leaves the gun
Motion of gun prior to bullet exit
Effect of recoil on the jump of revolvers
There's a graph of TEST RESULTS of center of group versus bullet
weight for various powder loads. Quote: "The heavier bullets always
shot higher than the lighter ones. The heavier powder charges did
not seem to make the groups any higher than the lighter charges".
He shows the calculation of how far the gun moves back before the
bullet leaves, and states "It will be observed that velocity
does not enter these equations". Powder weight does, but not
very strongly.
The discussion is similar to what was said here by
Louis J Boyd <bo...@pegasus.la.asu.edu> and
zcart...@aol.com (ZCarter530).
Hatcher does not try to calculate rotation. I have, and you
need additional info about the weight distribution, etc.
For a recoil-operated pistol I expect the effect to be less
than in a revolver in that the slide could mainly move
straight back (only a few millimeters) while the bullet is still
in the barrel.
Rotation (muzzle flip) after the bullet is gone doesn't affect
point of impact.
----------------------------------------------------------------------
Bruce Langdon L-472 u14...@nersc.gov
Physics Department
Lawrence Livermore National Laboratory, Livermore, CA 94550
Mark Gibson
In a previous article, brian....@sdrc.com (Brian Morgan) says:
#Wouldn't it make sense that the FASTEST bullet would drop the least?
#My assumption would be that they would both (slow and fast bullet)
#drop at the same speed (that gravity thing, Galileo, and all that),
#but the faster bullet would be farther from you as it drops. As a
#slow and fast bullet pass the target range, the slow bullet would
#have dropped further, because it took longer to get there.
# Just my logic...
# Brian
If the gun is held perfectly stationary as it is fired, what you say
makes sense. But when fired offhand, the slow, heavy bullet will
cause the muzzle to flip upwards more by the time the bullet is exiting
the barrel, so the heavy bullet gets launched on a different, higher
initial trajectory...which results in it hitting higher at typical
handgun ranges.
The same logic applies to identical bullets fired at different velocities.
Fast bullet should hit lower than a slow bullet of the same weight,
assuming typical handgun loads are used. I intend to experiment with
different loads behind 180gr bullets in my Glock 20 over the next
few weeks. I'm looking for a load that puts the bullet exactly where
I'm aiming (vertically, anyway) at 25 yards, given my regular grip on the
gun.
I'd really like to find someone with a Ransom Rest, so I can determine,
once and for all, to my own satisfaction anyway, that heavy bullets really
do hit higher than light bullets, all else being equal, at typical handgun
ranges. How much does a Ransom Rest cost, anyway? How much do the inserts
for each kind of pistol cost?
Mark Gibson
(NRA Life, 4/13/93;
10mm Preservation Society;
Glock Perfectionist)
--
===========================================================================
Mark Gibson | The Bill of Rights: Void Where Prohibited by Law.
gib...@prairienet.org | Gun control is hitting what you're shooting at.
| Vote Walter Williams for President in '96!
steve hix
# #
# What ranges are we talking about here. If the ranges are short, maybe this
# phenomenon is due to the simlpe fact that lighter bullets have a flatter
# trajectory, they do not rise as much as a heavy bullet, nor do they fall as
# much.
Not per unit time, they don't.
# If i'm right, as you increase your range out to where the bullets'
# trajectories' begin to fall again, the lighter bullets will impact higher than
# the heavier ones
The original post was about shooting to the same point of aim with a given
pistol at typical pistol range, probably under 75 ft.
nsco...@alpha.nsula.edu
# In article <444705$p...@xring.cs.umd.edu>,
# ZCarter530 <zcart...@aol.com> wrote:
# #
# # Center of mass is the relevant concept. The amount of time the
# #spends in the barrell has nothing to do with it. The weight of the bullet
# #*is*
# #what makes the difference.
# #
# Can't agree with this. Firing the same weight projectile in
# in the maximum hitting lower because the round left barrel
# quicker than the magnum.
#
# Jim
# --
# Jim Lentz Work ---> (le...@tellabs.com) Home ---> (le...@mcs.com)
#
# These opinions are mine (maybe) and not those of my employer.
#
What ranges are we talking about here. If the ranges are short, maybe this
trajectories' begin to fall again, the lighter bullets will impact higher than
-jeff
ZCarter530
#In article <444705$p...@xring.cs.umd.edu>,
#ZCarter530 <zcart...@aol.com> wrote:
##
## Center of mass is the relevant concept. The amount of time the
##bullet spends in the barrell has nothing to do with it. The weight of
##the bullet *is* what makes the difference.
#
#Can't agree with this. Firing the same weight projectile in
#.357 magnum and .357 maximum from the same barrel resulted
#in the maximum hitting lower because the round left barrel
#quicker than the magnum.
#
#Jim
Sorry to hear that you disagree with the basic laws of physics. : )
Check my other post, the relevant parameter in determining muzzle
rise is bullet weight * barrel length. The barrell length number which
enters is actually the distance the bullet travels from where it begins,
seated in the case, to where it exits the barrell.
The 357 maximum case is _significantly_ longer than the 357 mag
case, which means the distance the maximum bullet travels to the point
where it exits the barrel is shorter than the mag, thus giving less muzzle
rise according to the above formula.
I stand by my previous statement. Time in barrel has nothing to do
with muzzle rise.
ZCarter530
Ayers) writes:
#None of this is a theory, or subject to speculation! Lighter bullets
#print lower than heavier bullets. Writing about it a lot doesn't
#change the facts, or trying to suggest reasons why it isn't so doesn't
#change reality!
Nobody suggested reasons why it isn't so. The debate
was over WHY it IS so.
#Less time in barrel = less recoil-induced barrel rotation
False.
# The
#weights of the projectiles are irrelevant
False.
For readers interested in knowing the correct
answer to this question, I refer them to the 9/27 post
of Mr. Bruce Langdon ( u14...@sas-sun.nersc.gov )