Some questions back and forth regarding AKM/M70 bolt carrier replacements/compatability.   Essentially, yes, the AKM bolt face does interchange with the M70, as does the bolt carrier/piston assembly.  Some pix:

M21/AKM/M70 side by side


M21/AKM/M70 bolt carrier assemblies (M21 top, M70 middle, AKM bottom)



M70/AKM bolt carriers side by side (AKM is the beat up black one)

That's interesting the AKM mag lip doesn't look that much more fatter than the M70's. Unless this M70 was built for double stack mags.

They are all double stack, full auto rifles.   Find it very interesting to look at the different adaptations/dimensions.   The standard 7.62 AK mags fit perfectly, and lock up in the 5.56 M21.  A bit frustating when you are trying to get add'l mags, etc.