All of mine are Bushmasters but my brothers already bought two of the PO's so we're stuck with them. There was a thread on AR15.com that Kurt's Kustom Guns would modify your mil-spec bolt to fit for $60 including shipping back to you, then I searched for his contact and found he was killed in a motorcycle crash, I'm sorry for them. So I guess it can be done and the guy that had it done to his bolt said it ran great. I'll just keep looking, hate to scrap them and the wives and daughters just love them if we can get them running again.