If you're going to start loading for a gas gun, full length resize BUT, make sure you don't push the shoulders back too far. .001 to .002 is best. Too much working the brass and you'll end up with case head separation. Sooner or later, you'll run into that. No use rushing it.
I've loaded and fired at least 5000 rounds with RCBS full length dies for my M1A without issues. The RCBS Comp seater works like a charm as well as my Rockchucker press.
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