My 300/221 acuraccy needs to be better
I put together two 300/221 rifles (1:8 twist McGowan barrels, chambered by the same 'smith with the same reamer) and got a YHM-762 QD can and mounts for both. The AR was a challenge to get to cycle properly, but since lightening the buffer (rifle buffer/A2 stock), and switching to AA1680 powder, the thing cycles like a sewing machine.
The problem is now accuracy. In the AR, I've basicly duplicated the 300 Blackout load - 220gr SMK, 11.2gr AA1680, 2.089" OAL. I'm using Fed 205's in the Savage, CCI 41's in the AR. Today I tried 11.2, 11.3, and 11.4gr. I shot 10 shots each @ 100, suppressed. The 11.2 gr load was 3" wide, x 4" high, shotgun pattern. The 11.3 load was 2" wide x 5" high mostly in a vertical line, and the 11.4 load was the best at 2" x 2" most everything in a 1-1/2" group, but about 4 of these were going supersonic.
The Savage bolt rifle isn't doing much better with subs, but with 110-125 supers, is MOA @100. (I'm going to do some stock and trigger work on this one yet)
I've read on the 'net, that with subs, you don't want to put the bullet into the lands- -I assume due to pressure.
Is vertical that common with subs?
My next steps:
Neck size only (I know I can do this with the Savage, I'll have to test a few with the AR before loading a bunch), and see if that helps.
Work on the 11.2 load - I'm going to try a couple different seating depths, and see if that does anything. I'm thinking the reduced case volume might help?
Also going to try some magnum primers, to see if I can get better ignition.
Am I going in the right drection? What else can I try?
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