Recoil Effects on Vertical Spread (The Proof)
Jim Nasset
Over the past few weeks there has been a lengthy discussion on the effects
of recoil on the vertical dispersion of groups. My contention has been
that the recoil induced vertical spread in a group caused by the bullets'
travel down the barrel is "insignificant".
Those of you who wish to see the proof of my statement can go to my web
page at http://www.inventorworld.com/ami and check out two targets shot by
me in sanctioned hunter bench rest competition at Tri-Counties Gun club in
Oregon last spring. The vertical dispersion of 5 shots at 100 yards was
0.064 MOA, and for 5 shots at 300 yards was 0.169 MOA. The "horizontal"
group size is much larger as this was my first attempt at benchrest
competition, and I didn't pay enough attention to the changing wind
conditions. I simply shot at the bullseye on the targets each time.
The rifle used was a factory stock Rem. Mod 700 VS in .308 Win. Caliber.
The only change made to the rifle was to bed the recoil lug area (the H-S
Stock on it was "sloppy" in this area) and to install and tune the
AccuMajic Accurizer. The ammo used was 168 grain Federal Gold Medal Match.
If your rifle shoots a larger vertical spread than this, and does not have
a mechanical or bedding problem, then pay attention to your sight picture,
the mirage, heavy trailing or following wind conditions, trigger and
breathing control, the consistency of the velocities of your loads, and
finally tune your loads to your barrel, or your barrel to your load. Don't
chalk it up to the "myth" of rifle recoil induced inaccuracy.
Jim Nasset
Aftermarket Innovations
Robert Christman
Jim Nasset wrote:
#
# The rifle used was a factory stock Rem. Mod 700 VS in .308 Win. Caliber.
# The only change made to the rifle was to bed the recoil lug area (the H-S
# Stock on it was "sloppy" in this area) and to install and tune the
# AccuMajic Accurizer. The ammo used was 168 grain Federal Gold Medal Match.
#
Try this same test with a long barreled .45-70 or .50 Sharps cartridge.
There is an effect, it is often negligible when using high velocity
rounds. It is noticeable in some of the old black powder guns.
Besides, in a proper bench rest position, the recoil induced movement
should be roughly the same for each shot fired, therefore you won't see
any stringing effect. The problem comes in off hand shooting when a
shooter reacts differently to the recoil. Try sighting in your .308 and
getting it to where you get a good group off hand and then have someone
about 80 to 100 pounds lighter shoot the gun.
Bob C. NRA Endowment USN (Ret)
Jim Nasset
Robert Christman <rchr...@ix.netcom.com> wrote in article
<5g7qj3$g...@xring.cs.umd.edu>...
# Jim Nasset wrote:
# #
# # The rifle used was a factory stock Rem. Mod 700 VS in .308 Win.
Caliber.
# # The only change made to the rifle was to bed the recoil lug area (the
H-S
# # Stock on it was "sloppy" in this area) and to install and tune the
# # AccuMajic Accurizer. The ammo used was 168 grain Federal Gold Medal
Match.
# #
#
# Try this same test with a long barreled .45-70 or .50 Sharps cartridge.
# There is an effect, it is often negligible when using high velocity
# rounds. It is noticeable in some of the old black powder guns.
# Besides, in a proper bench rest position, the recoil induced movement
# should be roughly the same for each shot fired, therefore you won't see
# any stringing effect. The problem comes in off hand shooting when a
# shooter reacts differently to the recoil. Try sighting in your .308 and
# getting it to where you get a good group off hand and then have someone
# about 80 to 100 pounds lighter shoot the gun.
#
# Bob C. NRA Endowment USN (Ret)
#
#
Bob,
The .45-70 or .50 Sharps very possibly might have a substantially larger
extreme spread in velocity than more modern cartridges. I don't know as
I have never chronographed them. The same would probably apply to most
black powder rifles. This of course could result in a variation in
vertical spread.
As far as the recoil induced movement being "roughly the same" for each
shot
fired from the bench, I agree. And also "insignificant", in affecting
accuracy,
which was my point to begin with.
I don't believe that "off hand" shooting, could ever be used to demonstrate
the point
of vertical spread being significantly effected by recoil from the rifle.
The rifle simply
wouldn't be able to be held steady enough for a reliable test.
Best Regards,
Jim Nasset
Robert Christman
Jim Nasset wrote:
#
#
# The .45-70 or .50 Sharps very possibly might have a substantially larger
# extreme spread in velocity than more modern cartridges. I don't know as
# I have never chronographed them. The same would probably apply to most
# black powder rifles. This of course could result in a variation in
# vertical spread.
Back when the movie Quigley Down Under was out there was a question sent
to the AR about the accuracy of the Sharps. They proceded to do a very
nice article where they took a couple of quality replicas and went out
and tested them. They started with modern loads (smokeless powder) and
tested that, then carefully loaded a number of black powder cartridges
and tested them. One of the interesting discoveries was that the
velocity spread between cartridges was considerably lower with the
blackpowder rounds. The important point with these is that you are
talking low muzzle velocities and long barrels, which make any barrel
movement important - also remember the leverage, a couple of mils at the
muzzle is a lot at the target. As far as off hand shooting, most
hunting shots are off hand or at best a quick rest type shot. Recoil
does play a part of accuracy in this case. For bench rest shooting, it
is pretty much infintessimal, but not so in the off hand holds.
Michael Courtney
Jim Nasset (a...@inventorworld.com) wrote:
: I don't believe that "off hand" shooting, could ever be used to demonstrate
: the point
: of vertical spread being significantly effected by recoil from the rifle.
: The rifle simply
: wouldn't be able to be held steady enough for a reliable test.
Firing a small numer of rifles under controlled conditions is not
a general proof that recoil does not effect vertical spread in the
wide range of rifles and circumstances in which they are fired.
You're right that the off hand shooting experiment is not well-controlled
enough to be conclusive. However, it would not be too difficult to
perform a valid bench rest test which would show that the recoil effect
can be large in certain cases. For example, a comparison of the
impact point for the same aim point will probably show vertical stringing
for the following cases:
1) Butt of the rifle against a 1" high strip of rigid material rigidly
fastened to the bench.
2) Butt of the rifle against a 5" high sandbag.
3) Butt of rifle resting on a sandbag with nothing behind it
fot .25".
Michael Courtney
--
Michael Courtney, Ph. D.
mic...@amo.mit.edu
Doug White
Keywords:
In article <5gjkmd$f...@xring.cs.umd.edu>, michael@helium (Michael Courtney) wrote:
#Jim Nasset (a...@inventorworld.com) wrote:
#
#
#: I don't believe that "off hand" shooting, could ever be used to demonstrate
#: the point
#: of vertical spread being significantly effected by recoil from the rifle.
#: The rifle simply
#: wouldn't be able to be held steady enough for a reliable test.
#
#Firing a small numer of rifles under controlled conditions is not
#a general proof that recoil does not effect vertical spread in the
#wide range of rifles and circumstances in which they are fired.
#
#You're right that the off hand shooting experiment is not well-controlled
#enough to be conclusive. However, it would not be too difficult to
#perform a valid bench rest test which would show that the recoil effect
#can be large in certain cases. For example, a comparison of the
#impact point for the same aim point will probably show vertical stringing
#for the following cases:
#1) Butt of the rifle against a 1" high strip of rigid material rigidly
#fastened to the bench.
#2) Butt of the rifle against a 5" high sandbag.
#3) Butt of rifle resting on a sandbag with nothing behind it
#fot .25".
Recoil effects CAN be seen shooting offhand, but you have to be a
moderately good shot. I'm no Tubbs, but I shoot around 195 offhand at
200 yards with a .308. I have shot a bunch of commercial ammo loaded to
military specs, and a lot of match loads, which have noticeably less
kick.
If I want to shoot 195's with either load, I not only have to change my
elevation, BUT MY WINDAGE AS WELL. If the velocity difference was all
that was happening, I would only have to make a vertical adjustment.
Because your body twists from the recoil, the differing recoils produce
about a minute and a half of windage of difference in the group centers.
I shoot right-handed, and the lighter loads shoot to the left of the
higher recoil loads, as one would expect.
Doug White
Jim Nasset
Doug White <gwh...@tiac.net> wrote in article
<5gkf6l$h...@xring.cs.umd.edu>...
# Keywords:
# In article <5gjkmd$f...@xring.cs.umd.edu>, michael@helium (Michael
Courtney) wrote:
# #Jim Nasset (a...@inventorworld.com) wrote:
# #
# #
# #: I don't believe that "off hand" shooting, could ever be used to
demonstrate
# #: the point
# #: of vertical spread being significantly effected by recoil from the
rifle.
# #: The rifle simply
# #: wouldn't be able to be held steady enough for a reliable test.
# #
# Recoil effects CAN be seen shooting offhand, but you have to be a
# moderately good shot. I'm no Tubbs, but I shoot around 195 offhand at
# 200 yards with a .308. I have shot a bunch of commercial ammo loaded to
# military specs, and a lot of match loads, which have noticeably less
# kick.
#
# If I want to shoot 195's with either load, I not only have to change my
# elevation, BUT MY WINDAGE AS WELL. If the velocity difference was all
# that was happening, I would only have to make a vertical adjustment.
# Because your body twists from the recoil, the differing recoils produce
# about a minute and a half of windage of difference in the group centers.
# I shoot right-handed, and the lighter loads shoot to the left of the
# higher recoil loads, as one would expect.
#
# Doug White
#
Doug,
There are other things that you might consider that could cause the
horizontal
shift that you notice. The first is that the barrels harmonic vibrations
are changed
with the load change as well. This can cause the groups center of impact
to change both vertically as well as horizontally along with its size.
Also the
extra torque caused by the heavier load, due to a longer bearing surface of
the bullet,
will induce more cant in the rifle which must be made up for when sighting
in for the new load.
Just some thoughts,
Jim Nasset
Aftermarket Innovations
Doug White
Keywords:
In article <5gpicb$2...@xring.cs.umd.edu>, "Jim Nasset" <a...@inventorworld.com> wrote:
#
#
#Doug White <gwh...@tiac.net> wrote in article
<snip>
## Recoil effects CAN be seen shooting offhand, but you have to be a
## moderately good shot. I'm no Tubbs, but I shoot around 195 offhand at
## 200 yards with a .308. I have shot a bunch of commercial ammo loaded to
## military specs, and a lot of match loads, which have noticeably less
## kick.
##
## If I want to shoot 195's with either load, I not only have to change my
## elevation, BUT MY WINDAGE AS WELL. If the velocity difference was all
## that was happening, I would only have to make a vertical adjustment.
## Because your body twists from the recoil, the differing recoils produce
## about a minute and a half of windage of difference in the group centers.
#
## I shoot right-handed, and the lighter loads shoot to the left of the
## higher recoil loads, as one would expect.
##
## Doug White
##
#Doug,
#
#There are other things that you might consider that could cause the
#horizontal
#shift that you notice. The first is that the barrels harmonic vibrations
#are changed
#with the load change as well. This can cause the groups center of impact
#to change both vertically as well as horizontally along with its size.
#Also the
#extra torque caused by the heavier load, due to a longer bearing surface of
#the bullet,
#will induce more cant in the rifle which must be made up for when sighting
#in for the new load.
I think all of these effects are pretty minor compared to recoil motion.
Barrel vibration is probably not an issue, given that I shoot with an
extremely heavy barrel. I'm seeing sight changes of 3/4 MOA, which is
quite a bit. As far as the torque goes, I consider that a pretty small
effect, and in a sense, it's part of the recoil.
Doug White
Jim Nasset
Doug White <gwh...@tiac.net> wrote in article
<5grm41$5...@xring.cs.umd.edu>...
# Keywords:
# In article <5gpicb$2...@xring.cs.umd.edu>, "Jim Nasset"
<a...@inventorworld.com> wrote:
#
# #Doug,
# #
# #There are other things that you might consider that could cause the
# #horizontal
# #shift that you notice. The first is that the barrels harmonic vibrations
# #are changed
# #with the load change as well. This can cause the groups center of
impact
# #to change both vertically as well as horizontally along with its size.
# #Also the
# #extra torque caused by the heavier load, due to a longer bearing surface
of
# #the bullet,
# #will induce more cant in the rifle which must be made up for when
sighting
# #in for the new load.
#
# I think all of these effects are pretty minor compared to recoil motion.
# Barrel vibration is probably not an issue, given that I shoot with an
# extremely heavy barrel. I'm seeing sight changes of 3/4 MOA, which is
# quite a bit. As far as the torque goes, I consider that a pretty small
# effect, and in a sense, it's part of the recoil.
#
# Doug White
#
Doug,
I agree that a heavy barrel does lessen the harmonic vibrations more
than a light barrel, however it doesn't eliminate them. I have two heavy
bench rest barrels and a Rem. 700 VS also with a heavy barrel. With
the same load being used, I can vary the vibrational pattern in each, and
the group size and impact point (both horizontal and vertical) will vary
over an inch. I can also "free recoil" my 6BR and see virtually no change
in vertical or horizontal location, or group size, than when I hold the
rifle
against my shoulder. So this leads me to believe, that from a bench
anyway, that the effect of recoil on shot placement is negligible.
Best Regards,
Jim Nasset
Bill Oertell
Jim Nasset wrote:
#
# Doug White <gwh...@tiac.net> wrote in article
# <5grm41$5...@xring.cs.umd.edu>...
# # Keywords:
# # In article <5gpicb$2...@xring.cs.umd.edu>, "Jim Nasset"
# <a...@inventorworld.com> wrote:
# #
# # #Doug,
# # #
# # #There are other things that you might consider that could cause the
# # #shift that you notice. The first is that the barrels harmonic vibrations
# # #are changed
# # #with the load change as well. This can cause the groups center of
# impact
# # #to change both vertically as well as horizontally along with its size.
# # #Also the
# # #extra torque caused by the heavier load, due to a longer bearing surface
# of
# # #the bullet,
# # #will induce more cant in the rifle which must be made up for when
# sighting
# # #in for the new load.
# #
# # I think all of these effects are pretty minor compared to recoil motion.
#
# # extremely heavy barrel. I'm seeing sight changes of 3/4 MOA, which is
# # quite a bit. As far as the torque goes, I consider that a pretty small
# # effect, and in a sense, it's part of the recoil.
# #
# # Doug White
#
# Doug,
#
# I agree that a heavy barrel does lessen the harmonic vibrations more
# than a light barrel, however it doesn't eliminate them. I have two heavy
# bench rest barrels and a Rem. 700 VS also with a heavy barrel. With
# the same load being used, I can vary the vibrational pattern in each, and
# the group size and impact point (both horizontal and vertical) will vary
# over an inch. I can also "free recoil" my 6BR and see virtually no change
# in vertical or horizontal location, or group size, than when I hold the
# rifle
# against my shoulder. So this leads me to believe, that from a bench
# anyway, that the effect of recoil on shot placement is negligible.
#
# Best Regards,
#
# Jim Nasset
#
I'd be interested in the methodology used in obtaining "free
recoil." If in fact the results are valid, I'd say that the difference
between a rifle's center of gravity being held and not held, is
negligible, but this does not necessarily mean, then, that recoil has no
affect on vertical shot placement.
Bill
GEHCAT
Hi Y'all: If it is worth anything, my experience with my .44 Redhawk is
as follows: I was shooting some target loads using 9gr of Unique and 240
gr semi-wadcutters. I ran out of these cartridges and started using up
some mild .44 mag rounds, same slug but sitting on top of gas checks and
23 gr. of H4227. The H4227 rounds printed almost uniformly 4-5 inches
below the slower Unique rounds at 75 feet. I asked why and was told that
the difference was that the slower moving slugs were in the barrel longer
during the recoil. I took that on faith in the relator, but later I proved
it myself, to my satisfaction. Someone sent me some .44 rubber bullets to
be powered by primers only. At 20 feet, the rubber bullets hit 18 inches
below the point of aim. The reason the rubber bullets went so low was,
according to my lights, that there was no recoil at all with these
gadgets. Best to One and All, Maurice.
Grapeshot, n. An argument which the future
is preparing in answer to the demands of American Socialism. Ambrose
Bierce: "The Devil's Dictionary".