RE: which 7.62x39mm
I had a mini-30, and got rid of it. It would change zero from one day to the next. Shot small enough groups, but the group would be somewhere else tomorrow!! Also had two SKS, one a bring-back from the SE Asia Wargames, and the other a new Norinco that cost about $65.00. Both were more accurate and consistent than the Mini-30, but both "lacked charm". As to the 7.62X39mm being weaker than the .30/30, I suppose it is, but not enough to notice. For example, I have a load that shoots the Speer .311" 180 grain roundnose at about 1980 feet per second, which is more than the first .30/30 loads of a 165 grain at about the same muzzle speed. I like the 7.62X39mm cartridge. It is fun. But today, I'd be more inclined to look for a good bolt-action to shoot it in (CZ Model 527?? I believe).
Larry