From: sfaber@ihlpb.att.com (Steven R Faber)
Subject: Re: Ammunition for M1 Garand
Organization: AT&T

#From article <58431@mimsy.umd.edu>, by saksa@hplsdmc.col.hp.com (Tom Saksa):
# In a recent post I asked for information on ammunition for the M1
# Garand.  Here is a summary of the replies I received in the mail.
....
#
#    2. Dispite the durability of the M1, there are types of ammo that can
#    cause it problems.  The problems that were mentioned include the use
#    of surplus ammunition with corrosive primers, excesssive bullet
#    weights, or powder that has too slow a burn rate.  (Too slow a burn
#    rate, or too high a bullet weight can result in excessive port
#    pressure that can damage this type of gas operated rifle.
.....

A lot has been said about too slow a burn rate powder can cause excessive
gas port pressures, but I was thinking maybe a better way to look at
it is to look at the total powder charge weight.  Gas port pressure should
be proportional to the weight of powder used irrespective of the burning
speed of the powder.  It is just incidental that less powder is used
with fast burning powders too keep the peak pressure down and more
can be used with the slow powders.  Also it would not be related to the
mass of the bullet directly  - more like the muzzle velocity since the
faster bullets would spend less time in the region between the gas port
and the muzzle.  The quantity to look at for relative gas port pressure
would be the powder weight divided by the muzzle velocity.
#
#    3. The option mentioned least often was to shoot commercial
#    ammo.  However, this does not have to be much of a compromize.
#    It may be more expensive, and you have no control over powder
#    types, etc. but most M1 owners that replied found no problems
#    as long as they stuck to the lower bullet weights.  Also, if
#    you want to shoot the original ammo, some companies do sell
#    commercial .30-06 ball ammo.  PCM was mentioned as one such
#    company.

Maybe one could get a good idea on the commercial ammo by looking
at the powder weight to expected velocity ratio.


Steve

From: sfaber@ihlpb.att.com (Steven R Faber)
Subject: Re: Ammunition for M1 Garand
Organization: AT&T

#From article <58760@mimsy.umd.edu>, by brian@pdx.csd.mot.com (Brian Vandewettering):
#
# In article <58591@mimsy.umd.edu> sfaber@ihlpb.att.com (Steven R Faber) writes:
# #
# #A lot has been said about too slow a burn rate powder can cause excessive
# #gas port pressures, but I was thinking maybe a better way to look at
#                          ^^^^^^^^^^^^^^
# #it is to look at the total powder charge weight.  Gas port pressure should
# #be proportional to the weight of powder used irrespective of the burning
# #speed of the powder.
#
# Wrong!  Port pressure has *everything* to do with the speed of the powder.
# Granted charge weight has *some* influence on port pressure, but it's only
# marginal.  Loading reduced charges of slow powder can also cause detonation
# which blow up your firearm.

Just to make sure we are talking about the same thing, we are discussing
the pressure on the gas port system of an M1 Garand not peak chamber pressure.
The gas port on a Garand is only a couple inches from the muzzle.
The volume of gas generated by the powder is proportional to the charge weight
and independent of powder speed, so the pressure will be proportional
to the charge, since the temperatures will be relatively constant.
You will of course get some variation if you switch to double base powders,
but we were not considering unusual loads.
The above will still be true even if the powder detonates provided
the gun holds together.  By the time the bullet gets to the port
there will be the same amount of gas and the same pressure.
This is all just simple physics.

# #It is just incidental that less powder is used
# #with fast burning powders too keep the peak pressure down and more
# #can be used with the slow powders.  Also it would not be related to the
# #mass of the bullet directly  - more like the muzzle velocity since the
# #faster bullets would spend less time in the region between the gas port
# #and the muzzle.  The quantity to look at for relative gas port pressure
# #would be the powder weight divided by the muzzle velocity.

The discussion was about the relative strain on the gas system from using
fast powder loads vs slow powder loads.  Slow loads gave too much impulse
to the operating rod.  When I mentioned relative gas port pressure, I
should have said relative impulse on the operating rod.  I figured most
people would understand what I was saying, so it wasn't worth a correction.
The gas port pressure would be independent of the bullet mass also from
the above arguements, but the impulse on the rod would be the port pressure
times the time the pressure is in effect, which gives the formula :

# Please give us the source of your formula:
#
#  Port pressure = powder weight / muzzle velocity

better:
 gas system impulse = powder weight / muzzle velocity

# It sounds to me like this is a *theory* based on your own limited exposure
# to recreational shooting.

No just based on some simple physics and chemistry.

# DON'T give reloading advice based on what you *think*.  It may get someone
# hurt.

I don't remember giving any reloading advise except to suggest that it
would be possible to tell which commercial loads would be safe for
the gas system of a Garand by comparing the charge weight / muzzle vel.
ratio.
Maybe you should try *thinking* sometime too, its fun.:)

#
# <flame off>

Steve

From: sfaber@ihlpb.att.com (Steven R Faber)
Subject: Re: Ammunition for M1 Garand
Organization: AT&T

From article <59000@mimsy.umd.edu>, by smpod@ariel.lerc.nasa.gov (Stefan):
# sfaber@ihlpb.att.com (Steven R Faber) writes...
# ##by brian@pdx.csd.mot.com (Brian Vandewettering):
# ## sfaber@ihlpb.att.com (Steven R Faber) writes:
# # ...
# #Just to make sure we are talking about the same thing, we are discussing
# #the pressure on the gas port system of an M1 Garand not peak chamber pressure.
# #The gas port on a Garand is only a couple inches from the muzzle.
# #The volume of gas generated by the powder is proportional to the charge weight
# #and independent of powder speed, so the pressure will be proportional
# #to the charge, since the temperatures will be relatively constant.
#
# What makes you think that temperature is constant.  The powder is not
# instantly transformed into a gas.  For fast-burning powder, the pressure
# curve is peaked with a small tail, for slow-burning powder, the pressure
# curve is flatter with a high tail which is the cause for high pressure near
# the gas port.

The amount or speed of the powder won't determine the temperature of
the gas that gets created, since that depends on the heat of combustion
and the heat capacity of the combustion gasses.  There will be
some cooling as the gas expands but it is only a few hundred
degrees out of a few thousand.  Both the fast and slow powder
curves will have this cooling, so the difference between the fast
and slow curves temperature-wise would not be very big.
The reason the fast burning powder pressure curve has the small tail
is because you use less powder, and the reason the slow powder curve
has the higher tail is because you use more powder, because you are
concerned with keeping the peak pressure at the desired level.
If you take equal charges, the fast powder will peak sooner and higher
than the slow powder, but the tails will fall off to similar
levels.

# #This is all just simple physics.
#
# Internal ballistic is far from simple physics.  The transformation of
# solid to gas through combustion is not simple.

Maybe, but that equation I posted in Jan. was just simple physics, and
it does a pretty good job at reproducing the pressure and velocity
internal ballistics curves in the NRA fact book.


# People with experience in shooting and reloading for the M1, do not
# recommend any powder slower than IMR 4320.

OK, but isn't it because with powders slower than IMR4320 you start
using charges that are larger?   With 3031 you only need about 45 grains,
where if you used 4350, to get the same speed you would normally use
55 grains or so.  This would explain the higher gas port pressures with
the slow powders.

I think most shooters are used to thinking in terms of
powder speed all the time, where in this case charge weight is the
better indicator.

Steve

From: sfaber@ihlpb.att.com (Steven R Faber)
Subject: Re: Ammunition for M1 Garand
Organization: AT&T

#From article <1258@pdxvme.pdx.csd.mot.com>, by brian@pdx.csd.mot.com (Brian Vandewettering):
#
# In article <58946@mimsy.umd.edu> sfaber@ihlpb.att.com (Steven R Faber) writes:
# #
# # gas system impulse = powder weight / muzzle velocity
# #
#
# Let's take a look at the chamber presure over time for both a
# slow powder and a fast powder.
#
# max
#     xxx
#     x  x
#     x   x
#    x     x
#    x       xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
#   x
# 0 --------------------------------------------|------|
#                                               port   muzzle
#
# Fast Powder
#
# max
#        xxx
#       x    xx
#     x       xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
#    x
#   x
# 0 --------------------------------------------|------|
#                                               port   muzzle
# Slow Powder
#
# Note that the slow powder presents a higher pressure at the
# port which may exceed design specifications.

Yes, but isn't that because you are using more powder with the slow
powder because you can afford to due to the lower peak pressure?
If you have some data to indicate equal charges of fast and slow IMR
powders result in different height tails, then maybe I'll buy it, but
I don't think that is the case.


# Applying elementry chemistry and physics to this problem is like trying
# to calculate trajectory using first year calculus.  Also, you are assuming
# that the slow and fast powders produce the same amount of gas per unit of
# mass, however, the powders are made from different formulas.

You certainly have to be aware of where the simple assumptions break down
in trying to apply simple chemistry and physics equations, but in this
case I can't see a problem with my conclusions.  I don't believe there
is much of a difference in the composition of any single base smokeless
powder, except for some retardant coatings.  The speed variation
is obtained by varying the dimensions of the grains.
IMR 4831 is the same dimension as IMR 4350 but has a retardant.

Steve

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: Need Help RELOADING for an M1 GARAND!!
Organization: Hewlett-Packard Fort Collins Site

Reloading for the M1 Garand is much like doing so for any semiauto rifle.
There are three general rules you should follow:

  * Do not use powder that's slower than IMR4320.

    Doing so will create much higher than spec'd gas port pressures and
    that will put too much force on the operating rod.  This excessive
    pressure will be enough to bend the operating rod.  It can also
    cause the receiver to crack at the back as the bolt slams against it
    with too much force.  I've seen about half a dozen M1s that have
    been ruined by the use of too slow of powder; their owners thought that as
    this powder (4831, 4350) worked fine in a bolt action rifle, it would
    be fine for their M1.

    IMR4064 was the favorite powder when the M1 was extensively reloaded
    for to compete in highpower matches.  About 47 or so grains with a
    Sierra 168-gr. bullet was used to win a lot of matches.  Although 4895
    was used for both ball and match ammo as loaded by military arsenals,
    4064 produced much better accuracy and longer barrel life.  In addition,
    4895 is a fairly dirty powder and often requires barrel cleaning more
    often than when 4064 is used.  4895 was (and is) used in military
    ammo because it meters more uniformly in automatic powder measures than
    4064; for handloading and weighed powder charges, 4064 produces better
    accuracy.

  * Full-length size the cases, but do not set the shoulder back any more
    than about .003-in. from what a fired case measures.

    To do this, you'll need an RCBS Precision Mic, a great tool that lets
    you get the most reloads from your brass.  When the case shoulder is
    set back more than .003-in. from the fired case dimension, excessive
    case stretching will occur each time the case is fired.  This really
    shortens case life, and, in many situations, you get only 2 reloadings
    from a case.  By keeping the shoulder setback on fired cases from an
    M1 to about .003-in., you should get about 4 or 5 reloads from each
    case, then the case should be destroyed and trashed.

  * Seat the bullets out as far as possible to function through the
    magazine area, but ensure they are at least .020-in. back from the
    lands.

    This will enable the most accuracy the barrel will deliver.  It also
    prevents a bullet from jamming in the lands and staying there should
    you need to remove a loaded round from the chamber.

If your barrel's groove diameter is a bit on the large size, like about
3083 to .3087, Sierra and other US made match bullets may not shoot too
accurate.  With this large of groove diameter, the Lapua .3092-in. diameter
match bullets will probably be the most accurate.

I suggest you use commercial cases for best accuracy.  Although many folks
are enamored with the military cases with the word `MATCH' in their head
stamp, those cases are not very uniform in weight and thickness.

BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: M1 reloading
Organization: Hewlett-Packard Fort Collins Site

Kirk Hays (hays@SSD.intel.com) wrote:

: Depends on the factory load.  Federal makes a "Lake City Match"
: duplicate that is ideal for the M1.  Anything with a bullet weight
: over 160-165 grains is probably a no-no.

For years, the Navy's standard long-range load for 7.61 M1 match rifles
was:

  * LC case and primer; new.
  * 44 grains of IMR4320.
  * Sierra 190 seated about .050 short of land contact.

And boy howdy, did the rifle really kick!  But from prone, it was bearable
for 25 or so shots.  The most accurate long range load it was.

BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: M1 Rifles
Organization: Hewlett-Packard Fort Collins Site

Ron Phillips (crphilli@hound.dazixca.ingr.com) wrote:

: Bart, why?  I shoot 150 grains at DCM matches and 180 grains other times.
: Wasn' the "match" ammo used by U.S. Army snipers something like 179 grains?

Two things are going on here, I think.......

First, the standard USA military sniper rifle has been a bolt action rifle,
not a semiauto.  So bullet weight isn't an issue.  A few M14s were used as
sniper rifles and they used the M118 7.62mm NATO Match cartridge.

Second, the M2 30 caliber bullet (originated around 1920 for long-range
machine gun fire) weighs about 173 grains.  It was used in the older M72
30 Caliber Match ammo produced by Frankfort and Lake City Arsenals.
The same bullet was used in the XM118 and M118 7.62mm NATO Match ammo.
The M118 Special Ball sniper ammo uses the same 173-grain bullet.

BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: Rate of twist in .308 barrels
Organization: Hewlett-Packard Fort Collins Site

Christopher Morton (cmort@NCoast.ORG) wrote:

: What load do you recommend for the 190gr. Sierra in the M1?  I've been careful
: about using heavy bullets in my DCM gun, since I don't want to buy a lot of
: op rods.  I used to shoot 190s out of my Blue Sky and got better accuracy with
: them, although I suspect that was because of more bearing surface in the worn
: bore.

My comments about using 190-gr. bullets in M1s dealt with the 7.62mm version,
not the original 30 caliber M1.

Folks handloading for the 30 caliber M1 didn't have much success with bullets
heavier than 180 grains.  That was because the diameter of the gas port was
`tuned' for powders in the 4895-4064 burning range.  Using 47 or so grains of
IMR4064 with Sierra's 180-gr. match bullets was an excellent load; still is.
Use Rem. 9-1/2 or RWS5341 primers, then tune the powder charge for what gives
the best accuracy.  Bullets heavier than 180 grains need a powder slower than
IMR4320 to get decent, and uniform, velocity from a 24-inch .30-06 barrel.
Those powders cause too high a port pressure; enough to bend the operating
rod and/or crack the reciever's hump at the back.

BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: Rate of twist in .308 barrels
Organization: Hewlett-Packard Fort Collins Site

Christopher Morton (cmort@NCoast.ORG) wrote:

: So you're saying in essence that it would be POSSIBLE to make an M1 barrel in
: .30-06 with the correct port size for 190s?  Presumeably nobody DOES....

Some years ago, someone drilled a smaller gas port hole next to the one
in a 30 caliber M1 barrel.  He then tapped each port to hold a short set
screw.  His reasoning was that to shoot heavier bullets, the set screw
would plug the larger, original  gas port and let the smaller one transfer
a smaller amount of the higher-pressure gas from slow powders (4350 & 4831)
to the piston.  He reported it worked pretty well, but he was looking for
another barrel.  Seems he made the second gas port a tad too large and
sometimes the M1 would slam the bolt back too hard, but still with less
gusto than the original gas port would.

So, I think there may be a way to adapt the M1 rifle to functionally
work well with slower powders and heavy bullets.  I don't remember what size
hole he drilled for the second port.  As I remember, it was several
thousandths of an inch smaller.

BB