Are .22lr subsonic rounds more accurate than high or hyper velocity?
Chacon, Octavious A
In my reading of this group, it seems to be that subsonic loads are more
accurate than their high or hyper velocity brothers. Is this true? Could
someone explain to me why this would be? How would this have any relation to
a pistol versus rifle barrel lengths? Thanks:-)
--
Sincerely
Octavious Chacon
oac3...@rosie.uh.edu
Mechanical Engineering Student, University of Houston
and Glock 23 packin'
Cuidado con las armas,
Me las carga el diablo.
Alexander Eichener
But of course.
On 1 Aug 1996 oac3...@rosie.uh.edu wrote:
# In my reading of this group, it seems to be that subsonic loads are more
# accurate than their high or hyper velocity brothers. Is this true?
All .22 lr target ammunition is subsonic.
--
Alexander Eichener
c...@ix.urz.uni-heidelberg.de
Do not use aeic...@ix.urz.uni-heidelberg.de anymore (mail is forwarded).
The old VM address (c...@vm.urz.uni-heidelberg.de) is no longer valid !
Bruce Stanley
In article <31JUL199...@rosie.uh.edu>, oac3...@rosie.uh.edu (Chacon, Octavious A) wrote:
#In my reading of this group, it seems to be that subsonic loads are more
#accurate than their high or hyper velocity brothers. Is this true? Could
<snip>
#Sincerely
#Octavious Chacon
#oac3...@rosie.uh.edu
<snip>
I have tried various types of mainline .22LR in my BRNO MDL 4, Marlin 60, and
Browning Buckmark. The Remington Sub-Sonic rounds were more accurate than the
various High velocity and Hyper-velocity rounds in all of them (Winchester,
Remington, CCI, etc.).
I also tried some of the various "high-priced" Target rounds, including Eley
Ten-X, Fiochhi (sp?), and others, but couldn't see a marked improvement over
the "low-priced" Target rounds like CCI Green Tag or Federal Gold Medal - not
the handpicked variety (this was NOT a scientific test - outdoors, no set
cleaning pattern, etc. i.e. YMMV).
After the smoke cleared I bought mass quantities of the Federal Gold Medal and
Remington Sub-Sonic and haven't thought about it since.
-bruce
DOUGLAS HEARD
Subsonic rounds are more accurate because there is no lateral movement
when crossing the sound barrior (sp). High power rounds that get to the
target with out slowing below the speed of sound don't show this jump.
If you shoot a 30.06 far enough for the vel. to slow below the speed of
sound it to will have the jump.
.22lr High Vel. with a MV slightly over the speed of sound slows down in
a short distance. ( I haven't checked what distance & it would be barrel
dependent.)
I use subsonic when needed for accuracy and High Vel. for plinking
because of cost. If we used more subsonic ammo the cost would come down
but Americans always think faster is better.
In my Mosberg target rifle the difference at 50ft. is HV big one hole
group w/ standard vel. small one hole group.
In my 10/22 (stock not modified) Not all in one hole w/ HV and all in a
big hole.
Doug Heard
HS science teacher
Doug Owen
Chacon, Octavious A (oac3...@rosie.uh.edu) wrote:
: In my reading of this group, it seems to be that subsonic loads are more
: accurate than their high or hyper velocity brothers. Is this true? Could
: someone explain to me why this would be? How would this have any relation to
In general it is true. The best target ammo is sub-sonic (or very close)
at the muzzle in the type of gun it is intended to be shot in. The
theroy involves not only fighting the shock wave but transistioning to
sub-sonic, both variables in a system that doesn't tolerate variables at
all well. This is usually done with heavy bullets. Match ammo often
rides a few dozen fps from the mark. It is a matter of considerable
development, usually involving specific rifles. Clearly "no hold barred"
rifle ammo isn't optimum in any pistol, and the other way about.
OTOH, you've got to be shooting pretty good for this to be a factor. A
factory sporter probably won't know the difference between $10/box and
$3/box ammo. Heck, many with bedding and other problems shoot better
groups with some types of cheap (high speed) ammo, than say T22 or
similar "target" ammo. With these guns it is (as the Brit expression
goes) a matter of "suck it and see".
Doug Owen
Tom Aiken
Chacon, Octavious A wrote:
#
# In my reading of this group, it seems to be that subsonic loads are more
# accurate than their high or hyper velocity brothers. Is this true? Could
# someone explain to me why this would be? How would this have any relation to
# a pistol versus rifle barrel lengths? Thanks:-)
#
# --
As I understand it,(and if I am wrong, sombody tell me) there is a great deal
of turbulence created at transonic speed, meaning in the case of a bullet,
when it is slowing from a supersonic muzzle velocity through the sound barrier
to a subsonic velocity at which it hits the target. I imagine this probably
does affect accuracy, but to what extent I dont know.
Tom
--
My opinions are my own,
and have nothing to do with Lam.
jbur...@pipeline.com
I would have to say that it is because of turbulence that occurs as the
bullet is traveling at the sound barrier. I've noticed the same thing
happen to airgun pellets. If the arm was capable of shooting at sound
barrier level pellets had a wider spread at the point they were passing
through the barrier itself. Impact points were better before, and after
they had passed through the barrier. Current wisdom also holds that
subsonic bullets are less affected by the wind than tose traveling above
the sound barrier. Now why pellets would have a wider pattern at point of
sound barrier, and have better patterns after they had passed through it, I
don't know.
There seems to be more to this than the above though. I have a MAS45 that
thinks that CCI Stinger is match ammo at 50 yards, and gives ok performance
with green tag ammo.
Jim Burdine
au...@halcyon.com
# oac3...@rosie.uh.edu (Chacon, Octavious A) writes:
# In my reading of this group, it seems to be that subsonic loads are more
# accurate than their high or hyper velocity brothers. Is this true? Could
# someone explain to me why this would be? How would this have any relation to
# a pistol versus rifle barrel lengths? Thanks:-)
#
#
# Sincerely
# Octavious Chacon
In my limited understanding of the situation I understand the following to
be the reason that the subsonic round is considered more accurate.
For target shooting with a rifle the round leaves the barrel at its
maximum velocity. It then proceeds to lose speed during the flight to the
target.
If the distance to the target is such that the round slows from supersonic to
subsonic, it will undergo a degree of turbulence at the transonic realm, and
the resultant purterbations to the bullet will affect the accuracy at the target.
If the target is at the range that the bullet is still supersonic, no problem. If the
bullet starts subsonic, then the target range is irrelevant (mostly). So its easier
to calibate your long arm for one round, thats always subsonic, then mess
around with different rounds depending on target distance.
For most handguns the issue is moot, most pistol barrels don't allow supersonic
flight for most accurate ammo. Exceptions acknowledged!
but I could be wrong.
norm
geoff beneze
# In my reading of this group, it seems to be that subsonic loads are more
# accurate than their high or hyper velocity brothers. Is this true? Could
# someone explain to me why this would be? How would this have any relation to
# a pistol versus rifle barrel lengths? Thanks:-)
My theory is that that the lower velocities don't throw the bullets around
as much as the higher speeds. EVERY bullet has some imbalance here or
there. if you're going slower in speed, the rotation of the bullet is
less, thus throwing the bullet off less. At the higher velocity, any
imbalance, yawl or pitch in the slug is greatly magnified. Overall I've
sound that in all my rifles, the lower velocity rounds give better
accuracy than the higher velocities.
Of course, I may be way out in left field, but by my logic, this seems to
make sense, and my own testing indicates some validity to the theory.
--
geoff beneze
***************************************
* Arizona Shooting Sports *
* http://www.primenet.com/~geoffben *
* The UNOFFICIAL Dillon Support Page *
* ----------------- *
* NRA Life member *
***************************************
Nataliya Shub
## In my reading of this group, it seems to be that subsonic loads are
more
## accurate than their high or hyper velocity brothers. Is this true?
Could
## someone explain to me why this would be? How would this have any
relation to
## a pistol versus rifle barrel lengths? Thanks:-)
Hi,
All target ammo (R50, Tenex, Olymp-R, etc) are subsonic.
Walter Taylor
pos...@ix.netcom.com (Nataliya Shub) wrote:
### In my reading of this group, it seems to be that subsonic loads are
#more
### accurate than their high or hyper velocity brothers. Is this true?
#Could
### someone explain to me why this would be? How would this have any
#relation to
### a pistol versus rifle barrel lengths? Thanks:-)
#Hi,
# All target ammo (R50, Tenex, Olymp-R, etc) are subsonic.
#
The trans-sonic range is the area most likely to perturb a projectile
in flight hence if the initial velocity is near sonic velocity or will
drop into the trans-sonic velocity range, best accuracy will be achieved
with a sub-sonic load.
Walt
aur...@iamerica.net
geoff beneze wrote:
#
# In article <31JUL199...@rosie.uh.edu>, oac3...@rosie.uh.edu
# (Chacon, Octavious A) wrote:
#
# # accurate than their high or hyper velocity brothers. Is this true? Could
# # someone explain to me why this would be? How would this have any relation to
# # a pistol versus rifle barrel lengths? Thanks:-)
#
# My theory is that that the lower velocities don't throw the bullets around
# as much as the higher speeds. EVERY bullet has some imbalance here or
# there. if you're going slower in speed, the rotation of the bullet is
# less, thus throwing the bullet off less. At the higher velocity, any
# imbalance, yawl or pitch in the slug is greatly magnified. Overall I've
# sound that in all my rifles, the lower velocity rounds give better
# accuracy than the higher velocities.
#
# Of course, I may be way out in left field, but by my logic, this seems to
# make sense, and my own testing indicates some validity to the theory.
# --
# geoff beneze
# ***************************************
# * Arizona Shooting Sports *
# * http://www.primenet.com/~geoffben *
# * The UNOFFICIAL Dillon Support Page *
# * ----------------- *
# * NRA Life member *
# ***************************************
Is this why the U.S. Army has a 155mm cannon on the M1 Abrams main
battle tank that fires a projectile at over 6,000fps. This logic may
apply to .22lr, but I have doubts as to it's validity in any caliber of
appreciable size.
VC
*
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George Gehrke
Gentlemen: Sometimes human logic and science don't mix and I think this
is one of those times. Permit me to throw in .02 cents worth of
'reason'.
A bullet going at twice the speed of a sub sonic bullet spends less time
in a cross wind than the sub sonic bullet. Need I say more?
George Gehrke/Professional Sportsman
Steven Speer
George Gehrke (gin...@clarkston.com) wrote:
: Gentlemen: Sometimes human logic and science don't mix and I think this
: 'reason'.
: A bullet going at twice the speed of a sub sonic bullet spends less time
: in a cross wind than the sub sonic bullet. Need I say more?
Along the same lines, gravity _accelerates_ a bullet towards the ground.
The longer it's in the air, the greater the downward velocity componenet
and the greater the error at the target (even though the relative MV deltas
may be identical between the fast and slow round).
-Steve
Walter Taylor
s...@hpfcla.fc.hp.com (Steven Speer) wrote:
#George Gehrke (gin...@clarkston.com) wrote:
#Along the same lines, gravity _accelerates_ a bullet towards the ground.
#The longer it's in the air, the greater the downward velocity componenet
#and the greater the error at the target (even though the relative MV deltas
#may be identical between the fast and slow round).
#
# -Steve
#
Check your drag curves. Drag increases with velocity with a near vertical
step as the round goes through trans-sonic. Drop has no efect on accuracy
since gravity tends to be a constant in most places. Only shooting at a
target of unknown range will be effected by drop. Wind may be constant
or if you better than I, can be doped but is a shooter problem and not
a function of charistic accuracy. Ever hear of Kentucky windage and
Arkansas elivation?
Walt.
P.S. That step in drag is one of the effects that cause pertibations
in trans-sonic flight. Think of the buffeting that that aircraft
experiance in the trans-sonic transition.
Andy
Nataliya Shub wrote:
#
# ## In my reading of this group, it seems to be that subsonic loads are
# more
# ## accurate than their high or hyper velocity brothers. Is this true?
# Could
# ## someone explain to me why this would be? How would this have any
# relation to
# ## a pistol versus rifle barrel lengths? Thanks:-)
# Hi,
# All target ammo (R50, Tenex, Olymp-R, etc) are subsonic.
If subsonic rounds were more accurate how could target shooters shoot 1"
groups and smaller at 100 yards with the .308 Winchester for example. It
might be that you fire the .22 subsonic more accurately because there is
less noise to make you flinch as you squeeze the trigger.(22 LR ) Longer
barrels, to a point, give higher velocities. For target shooters the
object is not to hit the target really hard so there is no reason to
fire high velocity rounds There is likely to be a positive effect on
accuracy from low recoil and muzzle blast.
JaK
Stephen Swartz
In article <4uafn5$o...@xring.cs.umd.edu>, aur...@iamerica.net says:
#
#geoff beneze wrote:
##
## In article <31JUL199...@rosie.uh.edu>, oac3...@rosie.uh.edu
## (Chacon, Octavious A) wrote:
##
## # In my reading of this group, it seems to be that subsonic loads are more
## # accurate than their high or hyper velocity brothers. Is this true? Could
## # someone explain to me why this would be? How would this have any relation to
## # a pistol versus rifle barrel lengths? Thanks:-)
##
## My theory is that that the lower velocities don't throw the bullets around
## as much as the higher speeds. EVERY bullet has some imbalance here or
## there. if you're going slower in speed, the rotation of the bullet is
## less, thus throwing the bullet off less. At the higher velocity, any
## imbalance, yawl or pitch in the slug is greatly magnified. Overall I've
## sound that in all my rifles, the lower velocity rounds give better
## accuracy than the higher velocities.
##
## Of course, I may be way out in left field, but by my logic, this seems to
## make sense, and my own testing indicates some validity to the theory.
## --
## geoff beneze
## ***************************************
## * Arizona Shooting Sports *
## * http://www.primenet.com/~geoffben *
## * The UNOFFICIAL Dillon Support Page *
## * ----------------- *
## * NRA Life member *
## ***************************************
#
#
#Is this why the U.S. Army has a 155mm cannon on the M1 Abrams main
#battle tank that fires a projectile at over 6,000fps. This logic may
#apply to .22lr, but I have doubts as to it's validity in any caliber of
#appreciable size.
#
#VC
Hey Guys:
Maybe someone said this already but I think it is the transition (being
overtaken by you own shock wave) from supersonic to subsonic that upsets
the flight of the bullet. Whether the bullet (at the muzzle) is super or
sub sonic makes much less difference than whether or not it *stays that
way*.
A "supersonic" .22 won't stay that way for long; when it does go
subsonic (after 50-125 yards) it will "wobble" as it passes through the
shockwave.
The cure for this, as you may have guessed, is to give the bullet enough
muzzle velocity to make sure it stays supersonic all the way to the target.
The further away your target, and the lower your BC, the more MV you
need. If memory serves, for 600 yard shots and a BC of .50, you need
around 2700 fps . . . and, of course, for a tank, engaging targets out to
3000 meters and beyond, with a BC of .70 or so, you probably need a lot
more than that!
***********************************************************************
* =8^) * Abolish the welfare state AND the police state! *
* Steve * Which is worse: a Libertarian on food stamps; or *
* Swartz * a Socialist with a bank account? *
* * Support the ENTIRE Bill of Rights! Are you ok with *
* NRA Life * a well-armed group of religious-militia members *
* AFA Life * getting together to publish a newspaper calling for *
* * a return of power to the states? If not, you don't!*
***********************************************************************
Justin Tracy
In <4uafn5$o...@xring.cs.umd.edu> aur...@iamerica.net writes:
#*
Actually the Abrams has a 120mm smooth-bore gun, the projectile you
are refering to is a fin-stabalized sabot (pronounced say-bow)
penetrator so rotation doesn't come into play.
From what I've heard the inacuracy of .22lr high velocity rounds
comes from the transition from supersonic to subsonic speeds. Also,
wind actually has more of an effect on supersonic rounds because the
wind pushes on the shockwave. Of course if the round goes much above
mach 1 then the lower time-of-flight makes up for this.
Justin
Tom Aiken
# From what I've heard the inacuracy of .22lr high velocity rounds
# comes from the transition from supersonic to subsonic speeds. Also,
# Justin
Just get your self a mach4 .17 Remington/220 Swift and never worry about
that pesky transonic flight again. ;-)
Steven Speer
Walter Taylor (wai...@worldnet.att.net) wrote:
: #Along the same lines, gravity _accelerates_ a bullet towards the ground.
: #The longer it's in the air, the greater the downward velocity componenet
: #and the greater the error at the target (even though the relative MV deltas
: #may be identical between the fast and slow round).
: #
: # -Steve
: #
: Check your drag curves. Drag increases with velocity with a near vertical
: step as the round goes through trans-sonic. Drop has no efect on accuracy
: since gravity tends to be a constant in most places. Only shooting at a
: target of unknown range will be effected by drop. Wind may be constant
: or if you better than I, can be doped but is a shooter problem and not
: a function of charistic accuracy. Ever hear of Kentucky windage and
: Arkansas elivation?
Yes, but I don't see your point. Perhaps I didn't make mine clearly, and
perhaps I'm even wrong on this, but it's somewhat intuitive to me, so
let's try again. Two rounds are fired within a 50fps tolerance of their
mean velocity. One is travelling twice as fast as the other. Wind, as the
first respondent pointed out, has more time to use it's typically variable
force on the slower slug, introducing a larger error than it does for the
fast one. Perhaps not huge, but inherrently there.
I'm making the same observation for gravity. Yes, gravity is a constant,
but the vertical velocity component (which has nothing to do with aerodynamic
drag) is not. The slower bullet has been accelerated to a higher vertical
velocity than the faster bullet has, since gravity has acted on it twice as
long and it's a function of time squared. Now if they both exhibit the
maximum deviation from their standard velocity, 50fps, then the error caused
by gravity (vertical stringing) is greater for the slower bullet than it is
the faster one. Obviously, the lower the the velocity delta within a string,
the less this would come into play.
I haven't bothered to sit down and calculate what effect this will have,
but theoretically, it's there. To say that Drop has no effect on accuracy
pre-supposes consistent velocity. Somebody with a better handle on formal
physics calculations could actually quantify this for pistol vs. rifle
velocities and educate us all.
-Steve
Paul Thompson
In article <320A0C...@lamrc.com>, Tom Aiken <tom....@lamrc.com> wrote:
[snip]
#Just get your self a mach4 .17 Remington/220 Swift and never worry about
#that pesky transonic flight again. ;-)
Similiar (but unsimiliar) things happen with these calibers at the
trans-light barrier. Time dialation is a known problem with prairie dogs
(they can't read digital watches). ;-)
Walter Taylor
s...@hpfcla.fc.hp.com (Steven Speer) wrote:
#
#Yes, but I don't see your point. Perhaps I didn't make mine clearly, and
#perhaps I'm even wrong on this, but it's somewhat intuitive to me, so
#let's try again. Two rounds are fired within a 50fps tolerance of their
#mean velocity. One is travelling twice as fast as the other. Wind, as the
#first respondent pointed out, has more time to use it's typically variable
#force on the slower slug, introducing a larger error than it does for the
#fast one. Perhaps not huge, but inherrently there.
#
#I'm making the same observation for gravity. Yes, gravity is a constant,
#but the vertical velocity component (which has nothing to do with aerodynamic
#drag) is not. The slower bullet has been accelerated to a higher vertical
#velocity than the faster bullet has, since gravity has acted on it twice as
#long and it's a function of time squared. Now if they both exhibit the
#maximum deviation from their standard velocity, 50fps, then the error caused
#by gravity (vertical stringing) is greater for the slower bullet than it is
#the faster one. Obviously, the lower the the velocity delta within a string,
#the less this would come into play.
#
#I haven't bothered to sit down and calculate what effect this will have,
#but theoretically, it's there. To say that Drop has no effect on accuracy
#pre-supposes consistent velocity. Somebody with a better handle on formal
#physics calculations could actually quantify this for pistol vs. rifle
#velocities and educate us all.
#
# -Steve
#
The question was one of accuracy, not shootability (new word?).
The inherent accuracy of a round which may pass through the trans-sonic
regon is less then that which is not subjected to this same stress
thus target amo for the .22 rim fire is loaded sub-sonic. Shooter skill
is what the contest is about so the weapon and amo is selected to be
better then the shooter by as much as possable. Your statment of the
differences due to velocity are correct but the differences are not
great at the muzzle and with the higher drag, even less at 50 meters.
I did not want to make a war of this but there is a difference between
cartrage accuracy and problems of taking advantage of that accuracy.
Walt
funkraum
#DOUGLAS HEARD <DHE...@lc.gulfnet.com> wrote:
#Subsonic rounds are more accurate because there is no lateral movement
#when crossing the sound barrior (sp). High power rounds that get to the
#target with out slowing below the speed of sound don't show this jump.
[...]
As the bullet decelerates through the sound barrier, the centre of
pressure with respect to the center of mass, shifts forward.
Super-sonic flight exerts different aerodynamic forces on a body
compared to sub-sonic flight.
With this shift, the bullet gets a brief wobble while it restabilises
under the new forces.
Thus, accuracy is enhanced by staying on one side of the sound barrier
for the duration of the flight.
George Gehrke
Paul Thompson wrote:
#
# In article <320A0C...@lamrc.com>, Tom Aiken <tom....@lamrc.com> wrote:
# [snip]
# #Just get your self a mach4 .17 Remington/220 Swift and never worry about
# #that pesky transonic flight again. ;-)
A-MEN! But don't use it to just kill prairie dogs with. If you use it
for self-gradification only, then I can tell you where you should put
the barrel before pulling the trigger.
George Gehrke/Professional Sportsman
#
# Similiar (but unsimiliar) things happen with these calibers at the
# trans-light barrier. Time dialation is a known problem with prairie dogs
# (they can't read digital watches). ;-)
Michael Noyes
There was an article on this quite a while back in one of the
magazines. The conclusion that they came to is that high speed
bullets are no less accurate than low speed (subsonic) bullets
PROVIDED that the "high speed" bullet does not cross the sound
barrier during flight. The transsonic buffeting mentioned earlier
in this thread was the reason given. As few pistols fire a bullet
that travels much above the speed of sound this buffeting is a real
problem at ranges over 30 yards or so.
They did mention that wind deflection is lower with the faster
bullet, but the gravity argument doesn't hold water because the
difference in flight time with a 50 fps deviation would be on the
line of one thousandth of a second or less at pistol ranges. You
can't say that the extra time gravity has to act from the fast
bullet to the slow is a factor in accuracy, only the extra time
gravity has on the different bullets of the same base velocity.
The difference from fast to slow as far as gravity is concerned is
in point of impact, not accuracy.
Sorry for the long post, I hope I didn't tweak any noses out there.
Mike
Tom Aiken
The .308 is still supersonic when it hits the target. The drop in
accuracy is due to turbulence when the projectile slows through
the sound barrier.
--
My opinions are my own,
and have nothing to do with Lam.
Andy wrote:
#
# # All target ammo (R50, Tenex, Olymp-R, etc) are subsonic.
# If subsonic rounds were more accurate how could target shooters shoot 1"
# groups and smaller at 100 yards with the .308 Winchester for example. It
# might be that you fire the .22 subsonic more accurately because there is
#
# JaK
Steven Speer
Walter Taylor (wai...@worldnet.att.net) wrote:
The question was one of accuracy, not shootability (new word?).
I did not want to make a war of this but there is a difference between
cartrage accuracy and problems of taking advantage of that accuracy.
and then...
Michael Noyes (mno...@ix.netcom.com) wrote:
: There was an article on this quite a while back in one of the
: magazines. The conclusion that they came to is that high speed
: bullets are no less accurate than low speed (subsonic) bullets
: PROVIDED that the "high speed" bullet does not cross the sound
: barrier during flight.
(A point that Walt also mentioned).
: They did mention that wind deflection is lower with the faster
: bullet, but the gravity argument doesn't hold water because the
: difference in flight time with a 50 fps deviation would be on the
: line of one thousandth of a second or less at pistol ranges.
Both of you make good, but not directly relevant points. You're both
working from the assumption that the low velocity round is a pistol
round being fired at short distances. I read nothing in the original
post that caused me to assume this, it could be a .22 center-fire match
that's being considered and the range could be much longer than the
short pistol distances you guys are assuming it is. Even .30 cal slugs
can exhibit a virtual 2x in velocity. Compare a 7.62x39 with a 300 Weatherby.
When you're talking about very short distances, a lot of what it takes
to make something shoot accurately diminishes in importance, but that
doesn't mean the effects aren't real. The trans-sonic comments are completely
accurate, but don't really address the question. There are lots of things
that contribute to accuracy, but they are red herrings in addressing the
question of whether a slower cartridge has an *inherent* disadvantage in
accuracy. I simply pointed out that, theoretically, it does because of
gravitys disproportional effects on the velocity deltas each cartridge
*will* exhibit. I left quantifying it to someone else but since nobody
else volunteered and several have inaccurately characterized gravities
importance, I'll elaborate further.
: You
: can't say that the extra time gravity has to act from the fast
: bullet to the slow is a factor in accuracy, only the extra time
: gravity has on the different bullets of the same base velocity.
This is just plain wrong. It would be true if gravity induced velocity
was a linear function of time, but it's not, it's exponential. I'm not
sure exactly how to parse the second phrase in your sentence. I think
you're still trying to calculate point of impact for differing bullet
weights, but I'm not certain. In any event, it still misses the point.
: The difference from fast to slow as far as gravity is concerned is
: in point of impact, not accuracy.
This is only true if the bullets in a group are all fired at exactly the
same velocity. This is a pipe dream. Really good long range shooters
understand this effect and as a result, work to keep velocity VERY consistent
from shot to shot. But a higher initial velocity slug has a distinct and
measurable advantage over a lower velocity slug. This advantage increases
with increasing distance. Walt is, I believe, working from the same point
of impact perspective you are, that once you adjust for the distance, you're
done. I _think_ that's what he meant by "shootability".
OK, enough theory, that didn't work the first time. I didn't offer any
numbers last time because I don't have an easy way to calculate time of
flight, and this is, after all, the critical difference between two slugs
identical in every way except for initial velocity. I lucked out and found
some numbers in the back of my Nosler reloading manual (saving me the
exercise of exploring Hatcher who almost certainly offers more insight here
than any of us want) that tell us time of flight for the same bullet
fired at various distances and various velocities. Happily, it also shows
drop at various velocities.
Let's pick something somewhat practical, like a 150gr 30 cal Ballistic Tip.
The 300 mag class cartridges can easily throw this guy down range at 3450 fps.
Time of flight at 500 yards is about 1/2 second. Drop from a 200 yard zero
is -29.0 inches. The 7.62x39 will barely push this slug at the low end of
their table, which is 1750 fps. Time of flight in this case is a bit over
1 second, and drop is about -130.0 inches at the same zero. Note that gravity
has had twice as long to accelerate the drop on this slug. Many posting here
have said that this is the end of the story, you just have to hold higher.
The claim is that there is no "accuracy" issue here.
This can be shown to be false by taking note of the fact that no cartridge has
a zero delta in it's MV. To make it easy to use the tables, let's assume the
same +/- we were discussing before, 50fps. This means that we need to know
the drop for each cartridge in it's range of muzzle velocities. The 300 mag
drops 28.0 inches from it's 200 yard zero at 3500 fps (+50fps from mean) and
drops 30.0 inches from it's 200 yard zero at 3400 fps (-50fps from mean).
Time of flight is 0.52 seconds and 0.53 seconds respectively. That's a
2" vertical string attributable to a 1/100th of a second difference in flight
time. The only force acting on the bullet to cause this affect is gravity.
The 7.62x39:
drops 123.8 inches from it's 200 yard zero at 1800 fps (+50fps from mean) and
drops 138.9 inches from it's 200 yard zero at 1700 fps (-50fps from mean).
Time of flight is 1.06 seconds and 1.12 seconds respectively. That's a 15.1"
vertical string attributable to a 6/100ths of a second difference in flight
time. Again, the only force acting on the bullet to cause this accelerated
drop is gravity.
Now if you shorten the distance enough, this and many other questions about
accuracy become quite small. If you lengthen it, it becomes much larger.
The obvious answer for trying to minimize the effect at long distances is to
have as consistent a load as is possible, but I've yet to see one that's so
consistent that this effect is really zero. Even a +/- 10fps delta, which
is pretty good, will give a hi-velocity delta of a fraction of an inch and
a low-velocity delta of 3 inches or so. There is no escaping the fact that
when all other things are held equal, the lower velocity cartridge has a
measurable disadvantage to the higher velocity cartridge when it comes to
accuracy.
I don't really want to get into a dick jousting contest over this myself, I'm
just offering some insight to a factor I think many have overlooked in
addressing the question the original poster put forth. There are a lot of
cases, which I'm sure I'll get e-mail about from all the Camp Perry Wannabees,
where a slightly slower velocity cartridge will have a better overall accuracy
potential due to factors like more consistent MV, better case design, etc.
That's all well and good and I'm not arguing against any of it. I'm talking
about a single effect when all other things are held constant, the only
reasonable way to try to understand anything this complex.
-Steve
DOUGLAS HEARD
Thanks you did a much better job of explaining it than I did.
--
#############################
"Doug"
S. Douglas Heard
Stone Soup Canine Consultant
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Michael Noyes
I stand corrected. I switched away from rifle a few years back
(max range available 150yds, really accurate rifle, it was getting
boring) so my responses are predominantly based on pistol distances.
It is enlightening and thoughtfull discussions like this that keep
me hanging around.
Mike