In lots of digging around for information, what I've found is that most Garands operate best with heavier cast bullets, 180-220 grains. Yeah, some of you are screaming right now, but let me cover this:
The Garand was designed around 150-grain ball at ~2800fps. Cast bullets, including with gas checks, are a LOT softer than that standard jacketed bullet, and you're driving it at a lot lower velocity. So you can go to that heavy a bullet without putting strain on the system. What you have to do is juggle a few things(in no order of importance):
Bullet diameter
Bullet velocity
Gas port pressure
Standard bore for the M1 is .308; with cast bullets you normally size them at least .001" larger than the bore, depending on the particular gun and bullet/powder you might go up to .003" larger.
You cannot push a cast bullet anywhere near as fast as a jacketed. So you need enough pressure to make the bullet perform without pushing it too fast.
With a gas-operated rifle, if you want the action to cycle there has to be enough pressure at the gas port to do the job. Which is where the general Garand rule 'No bullets above 180 grains, no powder slower-burning than 'X'* allowed; violate either of those and you wind up with port pressure being too high, and you can wind up bending the operating rod. Bad enough on its' own, and can damage other things.
My original try was using the same 150-grain flatpoint bullets I load for .30-30. It took 35.0 grains of IMR4895 powder to make the action cycle reliably. Worked great, reasonable accuaracy but nothing to get excited about; good enough for shooting at the indoor range(30 yards) when couldn't get to the outdoor. So over time I've fiddled with some different bullet weights and diameters. A while back I picked up a Lee mold to throw a 30-caliber 200-grain gas-check bullet, and finally got around to casting some and making up two groups:
One sized to .309 and lubed with whatever I had in the sizing press(Lyman Gold in this case), and
One sized .311 and lubed with Lee Liquid Alox.
Different lubes because the largest sizing die I have for the Lyman press is .309, and I have a Lee .311 die setup that fits on the loading press.
The starting recommendation I read was 30.0 grains of IMR4895 and work up from there.
Some testing at H&H gave me some results to work with: 30 grains will cycle the action far enough to eject the empty, not enough to pick up the next round, for one, and probably the .311 bullet will work best. Put some together with 31 grains, and it chambered the next round sometimes, but didn't know if due to not quite enough energy or possibly the brass catcher dragging on the op rod(I hate losing brass**) So today took a set of loads out to try at 50 yards with a nice, solid bench:
HXP brass, 31.0 grains, .309
Federal brass, same powder and bullet
HXP brass, 31.5 grains, .311
Federal brass, same
And, just to try, some Korean PS brass with the 31.0 and .309 bullet.
Results:
This rifle doesn't care for Federal brass, at least with cast bullets.
The PS worked a bit better, but nothing wonderful.
Rifle likes HXP brass. A lot.
Rifle also likes the .311 bullet diameter.
31.5 will sometimes fully cycle the action, usually for the last 4-5 rounds
The scope I'm using runs 1/4" per click at 100 yards for adjustments; at 50 yards it took 32 clicks elevation to bring the groups from about 3" low to even with the bull. Not surprising, velocity is a good 800fps*** or more below that of ball. And- as I've seen in other rifles- the cast bullets hit a bit to the right.
Here's the HXP/31.0 load
Here's the HXP/31.5
Especially with me shooting, not bad at all. I'm going to up the charge by 0.5 grain in the next batch, I think that'll give enough pressure to reliably cycle the action, and should still have the bullet moving at safe(as in 'no nasty fouling') cast velocities.
Next time I'll hopefully be able to set up the Chrony, and will shoot at 100 yards. I'm looking forward to it.
And, to forestall a question, I just wiped the bore with a couple of damp patches(with the homebrew CLP) and there's no sign of lead fouling. I'll pull the gas cylinder later and check the piston.
*I can't remember that offhand, and I'm too lazy and tired to go look it up.
**I used the catcher I made for the M1 Carbine; works, but would need to be made a bit differently to fit the Garand properly. I've got a free-standing one I made for the outdoor range that avoids that.
***No chance to chrono the loads; the range was BUSY today.
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