I purchased this barrel thinking that it should fit with no problem but alas I was wrong. Seems to be a couple thousands of an inch to big at the clambering in end. My original pistol barrel is .60 and the 16.1 barrel is .62 the only barrel markings are the number 6770 stamped near the part where the barrel nut would cover. Is it safe to sand down to fit or should I just bail, sell it and purchase one from green mountain. Thanks for any responses.