Interesting. That thought has crossed my mind too. I know 1/2x28 generally isn't recommended for a 30 caliber bore, but people still do it, and even on 9mm. The problem with that is that my 30 caliber RIFLE suppressor is threaded 1/2x28. That's just what the manufacturer uses so it can be put on a standard AR. It does bother me how thin it is, but I've been told it is fine by the suppressor manufacturer. As for the twist rate, the barrel maker measured it down to the 1/4", so I trust his word that it is a 7 twist.
-Dan
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