Probably more than you really wanted to know…
Clem,
The ball powder used by LC in later M2 was WC852. It is sold in canister grade by Hodgdon as H380. Unfortunately, the military's bulk grade version of this powder came in two substantially different burn rates. Indeed,
this burn rate chart actually has two listings for the surplus bulk grade at positions 203 and 226, it was so different. The former required about 53 grains to reach M2 velocities, while the latter took more like 57 grains. The latter was too slow, making too much gas port pressure for the Garand's long, slender op-rod, but not wanting to surplus out the powder lot, the military made up a bunch of M2 with it that was qualified only for use in machine guns.
I have some of that machine gun M2. You can tell by the stripper clip marks on the cases and I have pulled down a good bit and changed the powder and bullets out to get better accuracy and spare the op-rod. The DCM, apparently unaware of this problem, issued this for the Garand, and while I don't know of an op-rod wildly bent by it, I am sure it was shortening life a good bit.
Several points about loading for the Garand:
People forget that modern electronics and high-speed counters didn't exist when the military was developing M2 ball for the .30-06. The slower vacuum tube electronics systems of the day needed more time to get the bullet's speed accurately. The timer start coil was at 6 feet from the muzzle and the stop coil was at 150 feet. The average of those two distances is 78 feet, so you will note the velocity data for the .30-06 is given as accurate at 78 feet, at which point it will have lost a little over 60 fps. So if you are measuring near the muzzle, that velocity number does not quite copy the original ammo. On the other hand, it must be born in mind that the velocity was measured coming out of a test barrel that is made to minimum specs and is carefully loaded so the powder in the case is falling back over the primer (it's maximum pressure and velocity position). You cannot expect your Garand to produce that same velocity. You need a different way to figure it out.
Here's what I did: First, some time ago I went through the M2 Ball ballistics data and found the bullet shape was best modeled by the G6 reference projectile, not the standard G1 projectile. It comes closest to providing all the right bullet drops and the right extreme range when you use a G6 BC of 0.212 from muzzle to the terminal point. If you use an exterior ballistics program that allows the G6 drag model, that will give you the most accurate results for that original bullet (flat base, 7 cal tangent ogive, weight of 152 grains maximum with a -3.0 grain tolerance).
The free calculators at the JBM Ballistics site allow this. If for some reason, you need the older standard G1 BC, it is about 0.387 over the first 100 yards. It drops off to 0.330 at 1000 yards because of the G1 projectile's drag curve shape mismatch. I have attached a PDF file of my work on this, with pretty complete lists of G1 BC v. range and velocity correction tables for the M2 bullet as well as sight come-ups for different muzzle velocities.
The second thing I did was use Hodgdon's published data for the 150 grain Nosler Ballistic Tip bullet. It won't be exact, but it's as close as we are likely to come without investing in a test barrel. They use a 24" pressure test gun, as does the military. The only difference is the military measures gas port pressure as well as chamber pressure. They have 150 grain bullets (close enough) and 15-foot velocity results (the SAAMI standard screen mid-point). From that, I can tell you what their test powder charge would be to get to military MV with the 150 grain Nosler bullet. This is easy because the number of fps/grain of powder is very linear within the published load range and even a short range outside it. So, velocity v. charge is a straight line within that range for all practical purposes.
Some data (note that this is all close to or slightly below published data for the closest bullet weight):
To go 2740 fps at 78 feet (26 yards), the M2 ball bullet needs a muzzle velocity of 2801 fps. At 15 feet (SAAMI chronograph distance) it will measure 2794 fps from a minimum chamber test barrel. Plugging 2794 fps into the straight line fit we get:
H380 -> 52.9 grains (just under their 53-grain minimum load, but is within dispensing error range. This is the faster WC852, so it should be OK in the Garand.
IMR 4064 -> 48.1 grains (This is about 1/4 of the range above the starting load).
IMR 4895 -> 47.4 grains (This is below Hodgdon's starting load of 49 grains, but is a typical Garand load charge weight).
Note that Hodgdon uses a Winchester LR primer. H380 is likely to work best with a magnum primer, like the CCI #34. This is because it is both harder to ignite and running at the low end of its pressure range. Note, too, that Hodgdon uses reference powders for testing. The lot you buy may be off on burn rate by a few percent, so, as always, work the loads up carefully.
If you want to use slower powders in the Garand, you need to use a modified gas plug.
I like this one, as you don't need to adjust it. Just shoot.
I have a
PDF file of 100 yard reduced sighting targets showing where POI for several loads would land at 100 yards when your sight come-ups are correct. Note that the 600 yard target is two pages that have to be joined after printing.
