[Tommo]

My Forster .308 Winchester headspace gauges are marked:

.308 Win. GO Gauge 1.630",

.308 Win. NO GO Gauge 1.634",

.308 Win. FIELD Gauge 1.638".

Myself, I only shoot 7.62 NATO ammo in most of my Armscorp and Springfield rifles which accept the NO GO Gauge 1.634". The only exceptions, I have shot Federal Gold Medal Match .308 ammo in my Armscorp and Springfield Match rifles with no problems. These rifles accept a Forster NO GO Gauge 1.634", but that is in my rifles and only with the Federal Match ammo!

I have read a rifle that does not accept a FIELD Gauge is safe to shoot, but it is your decision!

 

[Tommo]

I wrote I read it, I do not do it! Just trying to emphasize safety. First, it is a new M1A which most likely does not even have USGI parts. Second, you never know what kind of .308 ammo someone will shoot in their rifle, like reloads with 200grain hunting bullets! It is not unheard of for M1As to be damaged or blow-up with the wrong ammo, even ammo that might be safe in a bolt gun.

 

[Tommo]

If I was going to shoot .308 hunting ammo in my Armscorp or M1A rifle, I would use a round with a spire point 150 grain or 165 grain bullet. The reasons for this are:
1. The spire point bullet is very close in shape to military ball ammo bullets and this would help with reliable feeding from the mags.
2. The M14 type rifle's gas system is designed to operate within a certain pressure range and ammo with 150 grain and 165 grain bullets would more likely generate these type of pressures depending on the powder the rounds are loaded with. Rounds with heavier bullets like 180 grains or more might work, but they are harder on the action of the rifle because of the pressure they generate.

Keep in mind if you are reloading for M14 type rifles, you have to be more particular in your methods and component selection than for a bolt action. Most experts recommend using thicker military surplus brass, thicker military type primers and full length resizing of the brass with small base dies. It would be wise to use 150 grain or 165 grain hunting bullets with medium burning powders like IMR 4895 or IMR 4064. Use loads listed as safe in one of the popular reloading manuals like Speer or Sierra.

There are many posts here about reloading for these rifles and I recommend you read them very carefully.