Before anything else I have to say that my AK47's barrel is likely going to be replaced, even though the rifling is still strong.
I cast some 7.62x39 boolits (Lee C312-155-2R) and PC'd / gas-checked them, sized to .312":
Why? Because I had a .312 sizer but mostly (to my chagrin) because I "assumed" my bore size. Target at 25 yards with 2" stickers (and yeah, I know how to shoot):
To fix the shotgun-pattern, I went back home and added more and more PC to the .312" boolits (I had to coat/cool a further 3 times before they were at .314", even using Eastwood's Ford Blue) and got the tighter results in the pic to the right on the next day.
I know, still not great but 1) it's a really narrow bench (front to back is like 8" long) to rest on with zero support at the rear and at the worst possible height for me and 2) it was an experiment to see whether a) fatter boolits made a difference or b) whether the boolit-design just didn't suit my barrel.
I'm convinced enough that the design seems to be just fine (given the stable holes in paper, primarily) and I just need to get the size right. I'll undoubtedly get a new barrel soon, but in the meantime I'm having an interesting time experimenting and my results might be a good heads-up to anyone who may have some doubts that fit is king