Really good barrels - Faxon Firearms Match Series 9mm Luger, M&P Full Size Gen 1/2 Non-Threaded Pistol Barrel

I have 4 Faxon barrels in my M&P collection. A couple of those are threaded. I have experienced no problems, these fit good in the M&P slides. I keep reading reviews in which people complain about needing fitting instead of being drop in. From my experience, this is probably due to Smith and Wesson variances in their manufacturing. I know that there are mayor differences when I started to swap barrel between different slides. I was working with 15 slides at one time, both 9mm and 40. Randomly, some barrels do not fit some slides, etc. So I am convinced this is a Smith and Wesson manufacture variance or they have changed their internal specs from time to time. Very weird, but it is what it is.