The two issues with the 7.62x39 are the bolt and magazines. The Stoner mags work well, I use the 10 round mags for hunting. I wouldn't buy a mutant because of magazines!
The bolt is another specific part, and because the diameter of the case is about as big as the AR15 can handle, it has a reputation for breaking bolts. I haven't broken mine yet, but I don't run it hard though.
The Blackout is a good compromise, but it is not quite as powerful, and not nearly as cheap as steel cased 7.62x39. It does have a better selection of factory hunting ammo. Brass can be made from .223, but it is a chore.
I built my 7.62x39 upper before the Blackout was available, I reload for it for hunting. Today I'd buy a Blackout if I reloaded, and convert ,223 brass if I felt really cheap.
