"New"M1A barrel is junk.

[Punch The Clown]

I got My headpace gages and tested the Rifle I have been shooting...It flunked "harder"than Tom Selleck WAS in the magnum Years!I had to add several pieces of tape on the Field gage to stop the bolt,so it was a good thing I custom loaded each round to the chamber before I went out!

Barrel over indexed with hand tightening originally,,so I had to peen the shoulder for proper crush and according to My eye and laser level it is indexed correctly..Crap,now I have to save for another barrel I do not fear My reloads,I just want to be able to shoot factory loads whenever.
Ryan

Handloads won't make up for an un-supported case rim. Shoot 7.62 brass as it is much thicker.

[Punch The Clown]

Soooooooo, you might not have any problem here at all.

[Punch The Clown]

Okay, Gus Fisher talking now.

"For the 7.62mm: GO gage is 1.634" (the same as NO GO for the .308 Win.). NO GO is 1.638" (the same as the Field Reject for the .308 Win.). You will probably never find either spec. in military manuals, as they only list the Field Reject. The Field Reject is 1.6445". Now folks, that's a WHOPPING .0145", or 14 1/2 thousandths, over the minimum headspace for the .308 Winchester!!! To give you an idea what that means, the ENTIRE range of GO to Field Reject for the .30-06 cartridge is only .010" or TEN thousandths of an inch.
Therefore, even if you think you may have too much headspace in your rifle, you still may fall into the safety range of the 7.62mm cartridge."

[Punch The Clown]

And there's more . If you're using a Chinese or SAI bolt that may be your problem. Also, the bolt may have been lapped before it came to your possession. I'm done.