You may have to open the gas port. - Faxon Firearms 7.62x39 Russian Gunner Rifle Barrel

I got two of these running, and they seem fine, though I had to put the barrel on a drill press in 'V' blocks with a cleaning rod 'stop' to prevent accidentally going too far. I don't remember the final dimensions, but in my 'kit of everything' drill bits, I had to go up at least a couple steps to get the thing to cycle reliably with wolf ammo.

If you're not open to doing this kind of thing, while I like the barrel, I would suggest something else for 7.62x39.