Cast in .308 M1A - Help!!

[captain-03]

Using RCBS 308-165 SIL -- once checked and lubed, it is weighing in about 173gr. Using heat treated WW that test at about 29BHN with Lee tester.

I have tried 3 loads using the loading data provided in the RCBS Cast Bullet Book. I used 3 different powders (H110 - Red Dot - 4756). I stated with the minimum charged and worked my way up to the maximum charge using all three powders. None the of the loads will function the action on my M1A. Even with the max charge, there seems to be no indication of excess pressure - all rounds extracted easily manually - no flattened primers.

Anyone got a load for this cast bullet (or another between 173 - 175gr) that will function the action on an M1A?

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Parashooter]

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