Bipod and Accuracy Issue
CH
Remington Custom Shop and a 40x trigger installed.
It's a helluva shooter.
Here's the quandry:
With a Harris bipiod installed it has erratic groupings. From sandbag, or
with the bipod on a soft surface, it groups fine. It's not an issue with
the stock pinching in the front against the barrel, as it is free floated,
and I have tested that theory with a slip of very thin brass sheeting (to
check for evidence of pinching after shots). However, the poor grouping is
a persistent problem with the bipod installed and shooting from a hard
surface prone, e.g. cement/concrete.
My best guess is it's a recoil issue and the bipod is bouncing a bit. I
have swap the bipod with another identical one from a .223 and the results
are the same. In contrast, both bipods seem fine on the .223, though
obviously the recoil is much less.
Anyone with a similiar experience? Anyone with a possible remedy?
-CH
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nord...@yahoo.com
# a persistent problem with the bipod installed and shooting from a hard
# surface prone, e.g. cement/concrete.
# Anyone with a similiar experience? �
Yup.
# Anyone with a possible remedy?
Don't expect the same group size when you use the bipod on a hard
surface.
Flash
<nord...@yahoo.com> wrote in message
news:hef4ps$tq0$1...@news.albasani.net...
## poor grouping is
# # a persistent problem with the bipod installed and shooting from a hard
# # surface prone, e.g. cement/concrete.
#
# # Anyone with a similiar experience?
#
# Yup.
#
# # Anyone with a possible remedy?
#
# Don't expect the same group size when you use the bipod on a hard
# surface.
#
Well, it would seem to me that one possible remedy would be to make
extensions for the bipod out of some soft, easily flexed material that
retains a bit of rigidity and strength, something like a length of
heater-hose secured by hose-clamps. That way, you would have a reasonable
support, yet retain the ability to allow recoil without a lot of
restriction.
The cheap solution.
Flash
Louis Boyd
# I have a dandy Remington 700 LTR in .308
#
# My best guess is it's a recoil issue and the bipod is bouncing a bit. I
# have swap the bipod with another identical one from a .223 and the results
# are the same. In contrast, both bipods seem fine on the .223, though
# obviously the recoil is much less.
Next time you get on target with the bipod gently pull the rifle
straight back about 1/8 inch. Does the scope stay on target with the
accuracy you want?
If a bipod is set with the rifle forward of the bipod being
perpendicular to the bore it will jump up under recoil. If the rifle
is being perpendicular it will drop under recoil. If it's so far back
that it's close to the stops it will try to bend the stock on firing
and can do anything but ride straight back.
Try shooting it a little on each side of perpendicular and see what
gives best repeatability. The bipod must allow the rifle to move
straight back while the bullet is in the bore. Sandbags and benchrest
do. A 308 recoils about three times the distance of an equal weight 223
rifle before the bullets exit the muzzle.
For 10 lb (with scope and bipod) rifles with 24" barrels:
308 shooting 168 grain bullet at 2700 fps recoil at exit = .061"
223 shooting 55 grain bullet at 3200 fps recoil at exit = .021"
CH
# Well, it would seem to me that one possible remedy would be to make
# retains a bit of rigidity and strength, something like a length of
# heater-hose secured by hose-clamps. That way, you would have a reasonable
# support, yet retain the ability to allow recoil without a lot of
# restriction.
#
# The cheap solution.
#
# Flash
#
Someone locally suggest slitting tennis balls and placing one on each bipod
foot . . . not the most elegant solution :)
Jan Nielsen
<c...@cajunhawk.com> wrote:
>Anyone with a similiar experience? Anyone with a possible
remedy?
If your barrel is *just* clearing the stock you may still
experience contact during recoil, and a hard surface will
increase the bounce back through the bipod.
Try adding a temporary shim under the front lug to rise the
barrel slightly in the stock.
-JN-
Flash
Expand on this, Louis. Inquiring minds never thought of this - or point me
to a book??
Thanks,
Flash
Louis Boyd
# Expand on this, Louis. Inquiring minds never thought of this - or point me
# to a book??
Any book on precision shooting will tell you that shot to shot
consistency is the key to accuracy. A bipod will change the forces
applied to the stock if the legs are not free to move or if their angles
are changed between shots. Experiment with what angles give good
results then check that they're the same every shot. I don't know of a
bipod which does that automatically.
It's not much different from learning to shoot offhand accurately. That
requires consistent holds. That's only automatic with lots of practice.
Similarly in bench shooting the rifle needs to be set at the same
place on the rest and held the same for each shot. A consistent hold
is just as important with a bipod.
penultimate
> ...
Louis:
Upstream a bit you note fairly exact barrel recoil distances at the
time of bullet exit for the 223 and 308 and perhaps you can clarify
the equation giving origin to these particular numbers. Assumptions
would be nice to know too. For example, I imagine your numbers assume
unresisted expression of free recoil further restricted to exactly
that vector 180 degrees to the bullet path is assumed. I would
appreciate any elaboration you can provide because I am interested in
trying to apply a little math related to barrel time to see if I can
predict some of the shooting anomalies I observe.
I think your explanation of the "bipod effect" assumes that the bipod
"levers" the barrel to point in a different direction as it pivots in
response to recoil. If this is the case, I would note that the
"levering assumption" is unnecessary and that indeed bad things are
more likely to happen if the bipod legs are well-coupled to the
rifle. Think of the bipod as a significant mass attached to the rifle
eccentric to the vector of free recoil. The vector of expressed
recoil will thence be twisted or distorted by stationarity of this
eccentric mass in a manner similar to how an excessively pitched rifle
stock causes the barrel to jump upward on recoil or bullets from a
side by side double barrel rifle to cross. This would be obviously
observable if the rifle was somehow fired while hanging on a string.
The situation is worsened and exaggerated, and made more inconsisten
by any resistance provided by the ground to movement of the bipod
legs. A bipod will make shooting more accurate to the degree to which
it eliminates wobble in aiming but IT WILL ALWAYS MAKE THE RIFLE LESS
ACCURATE BECAUSE ITS ECCENTRIC MASS DISTORTS THE VECTOR OF RECOIL.
The issue is, of course, that lots of shooters naively think point of
aim at the instant of bullet ignition determines point of impact, a
fact generally good enough for government work, but less than
perfectly true if there is any inconsistancy in how the firearm is
held, canted, rested, and resisted by the shooter. In some cases, and
perhaps on a firearm-specific basis, the difference in even zero can
be quite large. For example, I have a 338 Win Mag which zeros about 5
MOA differently shot off a "lead sled" than when shot shouldered
normally at the bench. So, if some degree, for at least some rifles,
zero is influenced by the shoulder the rifle bangs into.
Louis Boyd
# Upstream a bit you note fairly exact barrel recoil distances at the
# time of bullet exit for the 223 and 308 and perhaps you can clarify
# the equation giving origin to these particular numbers. Assumptions
# would be nice to know too. For example, I imagine your numbers assume
# unresisted expression of free recoil further restricted to exactly
# that vector 180 degrees to the bullet path is assumed. I would
# appreciate any elaboration you can provide because I am interested in
# trying to apply a little math related to barrel time to see if I can
# predict some of the shooting anomalies I observe.
You can rely on conservation of momentum to determine the the velocity
of the rifle at the time the bullet exists the barrel. Determining the
time it takes for the bullet to leave the barrel requires knowing the
pressure curve on the bullet. Thats what an interior ballistics
calculator like Quicklload does. The math is not simple and requires
knowing the burn characteristics of the powder.
# I think your explanation of the "bipod effect" assumes that the bipod
# "levers" the barrel to point in a different direction as it pivots in
# response to recoil. If this is the case, I would note that the
# "levering assumption" is unnecessary and that indeed bad things are
# more likely to happen if the bipod legs are well-coupled to the
# rifle. Think of the bipod as a significant mass attached to the rifle
# eccentric to the vector of free recoil. The vector of expressed
# recoil will thence be twisted or distorted by stationarity of this
# eccentric mass in a manner similar to how an excessively pitched rifle
# stock causes the barrel to jump upward on recoil or bullets from a
# side by side double barrel rifle to cross. This would be obviously
# observable if the rifle was somehow fired while hanging on a string.
# The situation is worsened and exaggerated, and made more inconsisten
# by any resistance provided by the ground to movement of the bipod
# legs. A bipod will make shooting more accurate to the degree to which
# it eliminates wobble in aiming but IT WILL ALWAYS MAKE THE RIFLE LESS
# ACCURATE BECAUSE ITS ECCENTRIC MASS DISTORTS THE VECTOR OF RECOIL.
Accuracy is the same thing as repeatability. So I agree with all you
said. No rifle shoots at the exact position the barrel is pointed.
Rifles flex, wind blows the bulled, and gravity pulls it off course.
If all of those things happen the same with each shot including the
minute details of how a bullet copes with the atmosphere they will land
in the same place. There have to be forces on any rifle before
shooting it just to align it. As long as the forces repeat precisely a
gun will shoot accurately if other things in the gun like the burning of
the powder repeat precisely too. Skilled shooter insure a gun is held
the same way for each shot, whether it's by hand, from a benchrest, or a
bipod.
# The issue is, of course, that lots of shooters naively think point of
# aim at the instant of bullet ignition determines point of impact, a
# fact generally good enough for government work, but less than
# perfectly true if there is any inconsistancy in how the firearm is
# held, canted, rested, and resisted by the shooter. In some cases, and
# perhaps on a firearm-specific basis, the difference in even zero can
# be quite large. For example, I have a 338 Win Mag which zeros about 5
# MOA differently shot off a "lead sled" than when shot shouldered
# normally at the bench. So, if some degree, for at least some rifles,
# zero is influenced by the shoulder the rifle bangs into.
Those should all be obvious with just a little thought. Shoulders are
soft on only produce moderate force, especially in the first 1/16" the
rifle moves when while the bullet is in the bore. That typically takes
place 1 to two milliseconds. One of the first things you should
calculate to get an understanding of rifles is the force on the rifle
while the bullet is in the barrel. Its a simple calculation and the same
as the force on the bullet. It's just the propellant pressure times
the bore area. All other forces on a gun are relative to that. Pounds
per square inch times square inches equals pounds force. Adding a mass
tightly attached to a gun (like a bipod) produces forces higher than a
soft shoulder can. A benchrest does not produce much force during
recoil. But forces don't hurt accuracy if they repeat exactly in
magnitude and direction with each shot. Bipods can give decent
accuracy but they have to be used with as much care as any other form of
shooting to insure repeatability.
Bob Holtzman
............snip...........
# Bipods can give decent
# accuracy but they have to be used with as much care as any other form of
# shooting to insure repeatability.
If the recoil is such that the bipod legs lift off of the suppot surface
the chances of them coming back to the *exact* same place are miniscule.
If the surface is finished concrete, such as found on some benchrest
ranges, point of impact won't be affected *too much*. Any iregularity in
the surface and the recoil of the next shot won't be the same. So much
for repeatability.
--
Bob Holtzman
GPG key ID = 8D549279
"It's more fun when they go in the middle."
Herb Hollister cica 1960
Louis Boyd
# On 2009-11-28, Louis Boyd <bo...@apt0.sao.arizona.edu> wrote:
#
# ............snip...........
#
# # Bipods can give decent
# # accuracy but they have to be used with as much care as any other form of
# # shooting to insure repeatability.
#
# If the recoil is such that the bipod legs lift off of the suppot surface
# the chances of them coming back to the *exact* same place are miniscule.
# If the surface is finished concrete, such as found on some benchrest
# ranges, point of impact won't be affected *too much*. Any iregularity in
# the surface and the recoil of the next shot won't be the same. So much
# for repeatability.
Still, the advantages of a bipod can outweigh it's deficiencies.
Consider shooting from a moving platform or at moving targets. A
benchrest is a poor choice for either. It wouldn't be very practical
in combat or hunting to walk miles carrying and then setting up a
benchrest (and a bench) or sand bags before taking a shot.
Jim Bianchi
# Flash wrote:
# # Expand on this, Louis. Inquiring minds never thought of this - or point me
# # to a book??
#
# Any book on precision shooting will tell you that shot to shot
# consistency is the key to accuracy. A bipod will change the forces
# applied to the stock if the legs are not free to move or if their angles
# are changed between shots. Experiment with what angles give good
# results then check that they're the same every shot. I don't know of a
# bipod which does that automatically.
I'm only an egg, and I don't recall if the bipod was a Harris type
that mounts to the barrel as opposed to one mounting on the forward sling
swivel, but it appears to me if it is the former type, this will upset the
'natural frequency' of the bbl upon firing, which will in turn affect the
acuracy of the thing -- as that 'natural frequency' has been more or less
tuned (by bedding, ammo selection, etc) to give the desired accuracy.
--
ji...@sonic.net
Linux: gawk, date, finger, wait, unzip, touch, nice, suck, strip, mount,
fsck, umount, make clean, sleep. (Who needs porn when you have /usr/bin?)
CH
It's a Harris attached to a swivel stud. Hagning accessories from the
barrel . . . .shudder!
Bob Holtzman
# #
# # If the surface is finished concrete, such as found on some benchrest
# # ranges, point of impact won't be affected *too much*. Any iregularity in
# # the surface and the recoil of the next shot won't be the same. So much
# # for repeatability.
#
# Still, the advantages of a bipod can outweigh it's deficiencies.
# Consider shooting from a moving platform or at moving targets. A
# benchrest is a poor choice for either. It wouldn't be very practical
# in combat or hunting to walk miles carrying and then setting up a
# benchrest (and a bench) or sand bags before taking a shot.
Nnnoooo....really? Iirc the OP was talking about a zero shift with the
bipod vs that without. Tough to check that in the scenarios you cite.
--
Bob Holtzman
GPG key ID = 8D549279
If you think you're getting free lunch
check the price of the beer.
John Kepler
#
# Anyone with a similiar experience?
Just about anybody! Hanging stuff from the end of a firearm is never
a terribly good idea (it upsets the dynamic stability of the shooting
system), and your observed results are to be expected.
#�Anyone with a possible remedy?
Learn how to use an M1907 shooting sling? Works as good or better
than a bipod anyway without the "down-side"!
John
penultimate
> ...
Three cheers!
The utility of actually learning to shoot always trumps any offered by
a gadget, too many of which actually degrade the accuracy potential of
the rifle.
I am sure there are cases where a Harris-type bipod is actually useful
and am without comment as a combat or sniping aid. I am too old for
the former and disinterested in the latter. But a few comments on
hunting utility might be in order and hopefully will cause money to be
better spent.
In deer or elk or even antelope hunting IMO there are damned few shots
where claimed advantages of a bipod are not at least equaled by
opportunistic use of an environmental rest like a log, rock, tree, or
fence-post or a resting on something you are carrying anyway - for
example a small field pack. When I say "damned few", I mean I can't
think of ANY in the presence of a good faith attempt to recall every
game shot I have made shooting either prone or nearly so. And to
those that might point out that bipod legs can be extended for a rest-
assisted sitting or kneeling shot, I say good luck if you want to
diddle with bipod adjustments AND get into position before you shoot.
IMO you either won't have a target by the time all is in order or the
exercise was otherwise unnecessary because the shot was easily made
without the bipod (assuming you can shoot from a kneeling or sitting
field position) or because you had all the time in the world to pick
and take advantage of an environmental rest. Quickly recognizing
environmental rests and shooting quickly from field positions are
acquired skills that require practice. And, of course, the bipod is a
hinderance in addition to absolutely useless when it comes to a
standing shot. IMO you can count on a bipod always making the rifle
less pleasant to carry and hindering at least half the shots you might
otherwise take while providing virtually no necessary assistance to
the other half!
And for those otherwise wobbly shots on hind legs? John Kepler is
absolutely correct about a M1907 sling being a big help (and
reasonably quick) - assuming practice in its correct use. And for
those still in need of a gadget, shooting sticks are far more
versatile than a bipod and accommodate to reasonably quick use across
a much wider range of shot conditions. Cheaper too if you make your
own sticks and otherwise semi useful rubber banded together as a
walking stick.
For the record, I am dumb enough to have bought and tried a bipod
myself. All it took to realize it is in balance a big hindrance, at
least to my normal use of a hunting rifle, is toting the bipod
equipped rifle about in the field for a couple of hours while trying
to use it for "imaginary" (but responsible and normally plausible)
shots. Where you can often use some means of wobble reduction
(standing), the bipod was unusable. For sitting or kneeling shots,
the bipod slowed getting a shot off far to much and was without much
aiming value. For pure prone shots, it was neither a hindrance or an
advantage (relative to the backpack) - except that deer or elk hunting
don't that many firing lanes which are unobstructed from a prone
position. In virtually all instances where there was a good
environmental rest was available, the bipod interferred with its use.
And the damned thing made the rifle heavier and poorly balanced for
carrying!
CH
news:heutdq$1kq$1...@news.albasani.net...
> ...
I certainly don't disagree. When trapsing a wooded venue in pursuit of
furry food I would not want the weight or hassle of a stock mounted bipod.
My hunting weapons typically have 1" slings if offhand shots are required,
though my first choice for a rest is the aforementioned trees. Backpacks
are also excellent rests. I imagine shooting sticks could be handy if you
were in plains country, but I haven't had any experience hunting in such
terrain.
The original question was specific to a .308 rig that will likely never see
wood nor vale. At least I hope not considering the heft and optics setup.
Saint Augustine and a drag bag is about as close to nature as it'll get.
Dillon Pyron
> ...
That's what the other reindeer thought of Rudolph.
Perhaps just cutting the tennis balls up and using them as cups? Look
at 99% of the walkers out there. You'd think that after 30+ years
someone would have come up with something else.
Louis Boyd
# Thus spake "CH" <c...@cajunhawk.com> :
#
# > ...
#
# That's what the other reindeer thought of Rudolph.
#
# Perhaps just cutting the tennis balls up and using them as cups? Look
# at 99% of the walkers out there. You'd think that after 30+ years
# someone would have come up with something else.
30 years? The use of rifle mounted bipods dates back to at least World
War One. http://www.imfdb.org/images/8/89/Chauchat.jpg Bipods have to
be cheap and rugged for militaries to buy them. The US military is no
exception and they have used some just about as bad.
Just putting booties under a bipod won't cure it's problems.
Is there a market for a bipod which gives the precision of a bench rest?
Probably not. There are additional requirements to get benchrest
precision such as having a precisely fixed range, being able to monitor
downrange wind velocity variations with wind flags, and having
precision ammo tuned to the particular rifle. Reasonably designed
existing bipods are good enough for their limited use in sniping and
hunting that they don't add significant error to the point of impact
compared to other errors at distances and conditions in which they are
used.
Even setting up a benchrest and a bench in the field won't result in
"benchrest" accuracy in field conditions without wind flags. A $500
two ounce carbon fiber bipod with electronics to assist in setting it
precisely would probably give a detectable improvement over a Harris or
Parker Hale bipod, but who would buy it?
R.L. Horn
<dmp...@austin.rr.com> wrote:
# Perhaps just cutting the tennis balls up and using them as cups? Look at
# 99% of the walkers out there. You'd think that after 30+ years someone
# would have come up with something else.
Sounds like a business opportunity to me. Get some tennis balls made up in
unusual colors, get them Medicare approved, and charge $500 apiece for them.
Then, do some up in black and sell them to PDs with Homeland Security money
to spare. ;)
CH
walkers . . .
pyotr filipivich
about Wed, 2 Dec 2009 01:31:08 +0000 (UTC) did write/type or cause to
appear in rec.guns the following:
:
:Even setting up a benchrest and a bench in the field won't result in
:two ounce carbon fiber bipod with electronics to assist in setting it
:precisely would probably give a detectable improvement over a Harris
:or Parker Hale bipod, but who would buy it?
Someone with about 500 too many dollars burning a hole in their
pocket, and who had been convinced this would improve their shooting.
-
pyotr filipivich.
Just about the time you finally see light at the end of the tunnel,
you find out it's a Government Project to build more tunnel.