i got several kkm glock barrels in 40 s&w (4), 9mm (3), and 45 acp (1). only had this problem with one of the 40 s&w barre (g23)l. the round would drop into the barrel with the barrel removed. but when in the gun the gun would not go into battery. only had theproblem with cast lead. no matter what brand of cast lead i used. i looked into a tight chamber or short throat. i did the taper crimp them a more,short the round, etc..., worked like a dog to get the barrel to work with cast lead. then before i was going to mail it back to kkm i took the dremel tool and polished the insides of the chamber and throat. did most of the work in the area around the lands/groves. this worked, the barrel works with any and all cast lead.