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Cast in .308 M1A - Help!!
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05-21-2009 12:22 PM
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You need slower powder to get the port pressure where it belongs without excess velocity. Start around 30 grains of 4895 and work up until it just barely functions. If that won't group, try 4350 or 4831, starting about 35 grains and keeping an eye out for heaps of unburned powder clogging bore and chamber. Magnum primers sometimes help with low-density loads of slow powders. Going in the other direction, you could try around 20-25 grains of RL7, 4759, or AA5744.
What you are trying to do isn't easy and it's probably going to take a while to find a combination that both functions and groups. Harder alloy - pure Linotype - might help. Realistically, it would be a lot easier to switch off the gas valve and operate your M1A as a manual straight-pull with conventional fast-powder cast loads in the 1200-1600 fps range.
You'll find extensive discussion of M1A cast loads at that site where they can't spell "bullet" right - 7.62x51 NATO (.308 WCF) in the Springfield M1A - Cast Boolits
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