Hey all,
I have a May 1943 M1 and want to load for it. My research thus far has found imr4064 to be a safe powder for it. The Lyman 50th shows starting charge for 150s at 48.0. I know that needs to be reduced, but by how much? Please don't give the generic answer for military thick walled brass.
Does anyone have a reference or a published article about M1 Garand loads? If possible, using imr4064 and 155 grain bullets?
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https://www.ar15.com/forums/armory/I..._gr/42-413954/
There's a start for you. Not "published" data but it was posted in 2013 and has had no negative comments so far. Start 10% lower... etc.
And here's the thing with M1s... it isn't just the pressure that matters, it's where the pressure peaks in relation to the gas port.
M1 gas ports are very near the muzzle so a slow-burning powder like 4831 is still building pressure (that has to happen while the bullet is still in the barrel, right?)
until muzzle blast releases it. 4064 burns fast enough that the pressure peaks while the bullet is still only about half way down the tube, and the pressure is reduced
prior to the bullet passing the gas port. That way the operating rod isn't slammed rearward so hard it bends it. The very first surplus M1 part DCM ran out of was op rods.
You can find powder burn rate charts on the Net but they aren't linear... meaning just because powder number 97 is near number 98 doesn't mean it's safe to assume their burn rates are 'twins.'
You really have to extrapolate cleverly to use the charts. For instance, find loads of 2 powders that both develop the same pressure from the same charge under the same bullet, seated to the same depth....
and it's fairly safe to assume all powders listed between those two in the charts can be used too.
Yeah, unless you're a statistician you're probably going to want to find published data. But with field grade M1s going for a minimum of $700 it's worth the time to get it right.
Thank you!
I found a few topics on CMP forum and M1 garand forum. Those guys are running 4064 in a range where most are not exceeding 48 grains.
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