5/8-24 needs 0.623" and that is barely there (IIRC 0.628 was the measurement) on the Tikka T3X Light 6.5 the OP has cut to 21". The smith that threaded it wanted a damned shoulder and insisted it needed to be done 1/2-28" because of that. Once a (3/4" long) shoulderless 5/8-24 adapter was screwed on, there was the same RCH shoulder as it would had been cut 5/8-24 direct. Damned much ado about nothing. Thread them 5/8-24 and throw a locknut behind it. But, Thunderbeasts says minimum 0.725" barrel. Exactly why is that much shoulder "required"? BS, it's not, but then, what would there be to post about...


"I can't be canceled, because, I don't give a fuuck!"
--- Kid Rock 2022


Holocaust Deniers, the ultimate perverted dipchits: Bristoe, TheRealHawkeye, stophel, Ghostinthemachine, anyone else?