So I bought a Glock 19, Gen3, with suppressor height sights and a threaded barrel. Of course the barrel is threaded metric. Only in America. Even the Brits don't use metric. Why the hell would you sell metric shit in the land of SAE? Anyway, I bought an ATI threaded barrel with American threads and dropped it into the G19. Gun functioned fine unloaded. Threaded my suppressor onto barrel, hand tight, and now gun is locked up TIGHT! Slide will not move. Period! Backed off suppressor a few turns and gun functions normally. Retightened suppressor, same result. Suppressor touches nothing except the barrel. Backed off suppressor 3/4 of a turn and gun functions. Suppressor functioned fine on my Kimber. WTF??