I have a Model 1 Sales 7.62 x 39 upper for my AR rifle.  I haven't shot it yet but have come acrossed an interesting situation concerning the caliber.  I didn't know that Ruger's Mini Ranch Rifle which is made in the 7.62 caliber but with a .308 bullet diameter.  I am assuming that uppers for the AR rifles are made for the .311 bullet diameter.  That is the reason I bought the upper in the first place.  I would like to shoot surplus ammunition in it.  I called Model 1 and they said I could use either bullet diameter.   I was wondering what bullet diameter other AR upper manufacturers are suggesting.

Thanks for all answers in advance.

Terry

I shoot Wolf in my mini-30.

I don't think you will have a problem.

Mini 14's have a long tapered leade so the bullet is swaged down to fit the .308 bore. M1S might use the same thing.

Usually the "thicker" bullets in 7.62x39 are only .309-.310. I haven't heard anyone actually ever found any that had .311 bullets. Only true .311-312 bullets I've found are meant for .303 British.
I've measured some Wolf bullets myself and they were .309-.3095. Probably to make sure they won't cause dangerous overpressure in .308 bores. So generally this shouldn't be an issue, a couple of thousands thicker won't be hazardous unless the load is dangerous to start with and x39 is not a high pressure cartridge.