Lee C309-120 R in M1 Carbine Patterns Like a Shotgun

[milrifle]

M1-Carbine
Bore slugs .309 (Going from memory)
Throat slugs .310
Boolit dia:.311 (Beagled the mold)
Alloy: WCWW (21 bhn)
Lube: R5R's Simple Green
Charge: 10.0 to 12.2 gr 2400

I loaded up a few of these at 10.5 gr 2400. Don't recall OAL but was trying for slight engagement. I just did some plinking, but several would not allow the bolt to close without a little forward assist, so I seated a little deeper. This weekend, I decided to try to work up a load. I loaded 3 rounds each from 10.0 to 12.2 gr 2400. They grouped awful! At 50 yds, 10.4 gave me 1-1/4" group, but that was just a fluke. The rest were more in the 4"-5" range. It never even approached a decent group. Shot 3 factory loads and I could cover the group with a quarter. Tonight, I decided to do a pound cast. Throat measured .310.

What I think is going on is that the first driving band won't go into the throat and the nose is not big enough to do any supporting of the front end of the cartridge. All things being equal, I would try sizing to .310, but......I don't have a .310 sizing die. A couple of other things crossed my mind. Size .309 and hope they bump up? Use ACWW and size .309 and figure there's a better chance of them bumping up. Use ACWW and size .311 and maybe the driving band will manage to go into the throat?

What do you guys think?

[milrifle]

One other thing. Of the 3 round groups, the vast majority had 1 round near POA and 2 rounds tightly grouped but 3 to 5 inches to the right and later, on the higher charges, low and right, but one round near POA. I wasn't using a scope, so I don't know which rounds are which.

[Finster101]

I am using that boolit powder coated and sized to .310 over 12grns of 2400 and my carbine eats it up. Contact Buckshot and get a .310 push through sizer. You won't be sorry.

[ShooterAZ]

I size all my 30 Carbine boolits to .309. This is the only 30 Cal I own (Inland) that I have to do this for, and I think you just found why also. I would recommend 12.5-13.5 gr of either 296 or H110 sized at .309 and see what happens. .311 is obviously way too big, and don't seat the bullets to engage the rifling!

[Larry Gibson]

I've also found .309 to be the correct size for cast bullets (several different moulds) in multiple M1 Carbines. Suggest un - beagling the mould and sizing bullets at .309. The 12.2 - 12.5 gr 2400 should be an excellent load. Be sure the GC's are squarely seated and crimped on.

Larry Gibson

[milrifle]

Thanks guys. If .309 will work, that will be the easiest thing to do. Just hope I won't get any leading going that small. It will probably be the weekend before I get a chance to shoot. I'll see how it does.

Thanks again.