What you could do would be to have a sleeve machined to press fit on the muzzle where the threads are turned off - press it on and pin it. Then you could turn and thread that piece to whatever you want.
That's what I would do, but you need to yank the barrel out to do it.
Thanks for response---It had a cap tack welded on the muzzle with the detend unit--took the cap off NO THREADS--strange---would not the 1/2 X 28 threding work & look more professional? Would pay reasonable amount for turn-key job, or may just leave it. It is the RPK version which looks better with a muzzle brake.
Yeah, as long as you had at least .495 diameter, 1/2 X 28 would work - just be careful that whatever muzzle device you install has enough room to pass a .310 bullet.
I would be happy to do a turn-key job, but I don't have a full-blown FFL yet (working on it), and god knows if an unlicensed person performed gunsmithing without the bureaucrat's permission - the nearest five schools and nursing homes would explode!
So, if you can get someone local to pull the barrel, I'll thread it for $35 - take me about 15 minutes.
Sharky--Was told you do not need a FFl to work on guns----only when you buy & sell----dont work on cars or guns--How about $50.00 you do it all--live a little west of Austin---
OK--thanks for your input---will leave it as is--pretty impressive as it is with the long barrel, bipod and reflex sight by ATN. Has a Dracanov stock which the cheek piece heeds some elevation without the fist under--keep me in mind to do this modification