I load for both an M1A Squad Scout and a Winchester M70 FWT Stainless. I loaded for a Remington 700 VSFS for several years as well.
First of all, my M1A came with a card telling me that my rifle was headspaced at 1.632. The owner's manuel says that my rifle is cleared to fire all commerical .308, except the extra velocity ammo.
I've shot both loads for each in the other rifle. The M70 loads wouldn't chamber a few times. But all the ammo that my Lyman Case Gauge says is OK, chamber fine. All of the M1A ammo chambers and shoots fine in the M70.
The funny thing is the commerical .308 brass won't full lenth size small enough to function reliably in the M1A if it's been reloaded much. Even if most of it has been just neck sized with a Lee Collet Die and then full lenth sized. But the PPU and Lake City brass has always resized just fine.
So this isn't much of a problem. Heck, my Remington 700 ammo wouldn't chamber in my M70. But I could use the 70's ammo in the 700.
What I've found is I need to develop loads for each rifle with brass that works well with it. In the M1A, since you must full lenth size each time you reload it, you should use the heavier brass. You aren't going to load it very hot either. The rifle will eject extra hard and the accuracy, at least in mine, goes down hill fast if I try to load it hot. E
