I was under the impression that newer RPK versions had a birdcage of sorts.An RPK uses a muzzle nut (early milled or some stamped) or most common a slant brake same as the AKM. They are common and CNC should have either/both.
How about the RPK201?Only the RPK74. Not the 7.62x39.
That's the oneIf you are referring to the VEPR IV clone? Pretty much same as the AK74.