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I have an M1A that I have yet to buy ammo for. I have read a lot of mixed reviews about using 7.62 vs .308. Some people say they are all the same and other people (along with SA) say that you should stick with the 7.62 NATO rounds "because the primers are tougher and reduce the risk of premature firing when the bolt goes forward" I heard anything from 147-180 is recommended and to stay away from soft points. My question is for all you M1A owners, what type of ammo do you guys run through your rifles?
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I would suggest paying attention to what the manufacturer recommends for their rifle.
I shoot my reloads through my match rifle. I am very careful to use powders with appropriate port pressures and bullets that do not exceed 175 grains.
Your rifle was designed to function with ammunition originally loaded with IMR 4895 and 150 grain bullets and 175 grain bullets.
Velocities for the 150 grain bullets were around 2700 fps and followed this pressure curve
That inset, with the pressure drop, that is absolutely critical to the proper operating of this rifle. Too slow of a pressure drop gives high port pressures and hard extraction.
The 175 grain loads were not hot by today’s standards. And that velocity max of2550 fps, is real. It is what I have chronographed with white box ammo in a match M1a.
Powders slower than IMR 4895 are liable to over accelerate the operating rod. Since the bolt rebounds off the receiver heel, repeated hard impacts are hard on the sidewall of the receiver.
This is a Garand receiver with a cracked sidewall, but rest assured, it happened with M14’s and M1a’s.
With bullets heavier than 175 grains it is also easy to have excessive port pressures.
Unless the ammo box says it is OK to use in a M1a, you can assume every commercial round you buy was loaded for bolt rifles. Bolt rifles don’t have port pressure issues. Many commercial rounds are “magnum” level, you don’t want that in your rifle.