Fire form 7.62x39 ??

[Lemonaid]

I would suggest making one dummy round and see how it chambers, or if you can safely do it with your loaded rounds. If they wont chamber or are very hard to chamber you may have to adjust the sizing die to the maximum. If your are working with new unfired brass you should be o.k.
Another cause of hard chambering could be oversize neck o.d.
Hope it works out for you, Large rifle primers can increase velocities quite a bit so factor that in.
It is amazing how fast the world has gone crazy!