Shooting Sports USA - August 2014 - 32

FEATURE // VMR RELOADING
listed as a 50-grain charge.1 This next bit is
extremely important, and the reason why there
is sometimes confusion over powder charge
weights in military .30 caliber ammo. Though the
Army ostensibly set IMR 4895 charge weights at a
nominal 50 grains, the powder charge weights
in the M2 and M72 loadings actually varied over
the years because of variances in the burning
properties of different lot numbers of powder.
Interestingly, in the nine years of M72 production
using IMR 4895 (1957-1966), the charge weights
apparently never even reached 50 grains, instead
varying from 46 to 48.5 grains.4
Another place where confusion arises and elicits naughty words from anonymous gun forum
posters is with other military ammunition used in
the Garand. Tracer ammunition utilized IMR 4895
or WC 852. Armor piercing and armor piercing
incendiary ammo used WC 852 powder. The frangible round was loaded with SR 4795; the blank
round for launching grenades used 45 grains of
IMR 4895; and the standard proof test round was
loaded with 52 grains of IMR 4198 for that wincing
67,500 psi of overpressure.1 I've seen forum posters ask about these loadings, but none of them
are appropriate for duplicating M2 or M72 loads,
though it's interesting to note that the grenadelaunching blank round is in the ballpark.
Powders, of course, burn at different rates
(speeds), producing not just different peak pressures, but also differing in the amount of time it
takes to reach a maximum pressure level. This is
why we have "fast" powders for pistol cartridges
and "slow" powders for magnum cartridges.
If peak pressures were our only concern, there
would only need to be a handful of different
powders out there. Instead, we have more than a
hundred to choose from, and they are classified
by burning rate-fastest to slowest.

In the Garand, a too-fast powder can produce
too much pressure before it sends the bullet
downrange at a decent velocity. A too-slow powder may not get you the velocity or the pressure
you need. Powders with a burn rate appropriate
for the Garand are those between IMR 3031
(fastest) and IMR 4320 (slowest).
According to the Hodgdon chart of propellant
burn rates, there are 22 different powders available that fall within this parameter. IMR 4895,
used in the M2 Ball and M72 Match loads, falls
smack in the middle of the group and it's a logical
place for handloaders to start-and finish, for
that matter, unless you want to fine tune a match
load or are entertained by reinventing the wheel.
Keep in mind that trying to work up an awesome
match load for an ordinary surplus Garand
becomes a pearls-before-swine thing at some
point, because the battle rifle is not a precision
accuracy machine.

Bullets
Changing the powder charge will obviously
change the gas pressure, but so will changing
the bullet weight. Generally, increasing the
bullet weight increases pressure. This is why
we typically see a charge of any given powder
decrease as bullet weights go up. For example,
using Lake City Match brass and IMR 4895,
48.5 grains of the powder gives a 150 gr. bullet
2711 fps of muzzle velocity. Changing to a 190 gr.
bullet gives us 2571 fps with 46 grains of powder.1
Note the loss in velocity necessary to keep pressure levels acceptable with the heavier bullet.
Unlike M2 Ball, neither bullet nor primer are
heavily crimped in place in the M72 match loads,
but they're seated solidly enough to withstand
the recoil and cycling of the Garand action

TABLE: Comparison of Allowable U.S. Government M2 and SAAMI .30-'06 Pressures
M2 Ball
max psi

SAAMI
.30-'06 max psi

M1 Garand
proof psi

SAAMI .30-'06
proof psi

50,000

60,000

67,500

86,400

32 SSUSA AUGUST 2014



Shooting Sports USA - August 2014

Table of Contents for the Digital Edition of Shooting Sports USA - August 2014

Contents
Shooting Sports USA - August 2014 - Cover1
Shooting Sports USA - August 2014 - Cover2
Shooting Sports USA - August 2014 - 3
Shooting Sports USA - August 2014 - 4
Shooting Sports USA - August 2014 - 5
Shooting Sports USA - August 2014 - Contents
Shooting Sports USA - August 2014 - 7
Shooting Sports USA - August 2014 - 8
Shooting Sports USA - August 2014 - 9
Shooting Sports USA - August 2014 - 10
Shooting Sports USA - August 2014 - 11
Shooting Sports USA - August 2014 - 12
Shooting Sports USA - August 2014 - 13
Shooting Sports USA - August 2014 - 14
Shooting Sports USA - August 2014 - 15
Shooting Sports USA - August 2014 - 16
Shooting Sports USA - August 2014 - 17
Shooting Sports USA - August 2014 - 18
Shooting Sports USA - August 2014 - 19
Shooting Sports USA - August 2014 - 20
Shooting Sports USA - August 2014 - 21
Shooting Sports USA - August 2014 - 22
Shooting Sports USA - August 2014 - 23
Shooting Sports USA - August 2014 - 24
Shooting Sports USA - August 2014 - 25
Shooting Sports USA - August 2014 - 26
Shooting Sports USA - August 2014 - 27
Shooting Sports USA - August 2014 - 28
Shooting Sports USA - August 2014 - 29
Shooting Sports USA - August 2014 - 30
Shooting Sports USA - August 2014 - 31
Shooting Sports USA - August 2014 - 32
Shooting Sports USA - August 2014 - 33
Shooting Sports USA - August 2014 - 34
Shooting Sports USA - August 2014 - 35
Shooting Sports USA - August 2014 - 36
Shooting Sports USA - August 2014 - 37
Shooting Sports USA - August 2014 - 38
Shooting Sports USA - August 2014 - Cover3
Shooting Sports USA - August 2014 - Cover4
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