There are factory 7.62x39 rifles made with .308" bores. They shoot .311" bullets with no ill effects. The bolt actions Ruger made in this caliber have .308" bores, the bullets just swage down, .003" is not much and will not cause problems. I am not sure if Ruger Mini30s have .308" or .311" bores, but I suspect they are .308".
I am interested in a .7.62x39 bolt action also with a .308" bore. I have ordered the reamer and gauges from Pacific tool and gauge in the last couple of weeks. This is on the list for this winter's projects.
What a great way to use up some of that cheap surplus ammo in a nice little bolt action plinker. I had one of the Norinco 7.62x39 bolt actions and it was a complete piece of junk and waste of money.