This is the only problem I'm having with my M40A1, but it happens way to frequently. The gun locks right before it goes completely into battery. You can still pull the trigger but all you get is a light primer strike. To get the live round out, you usually have to knock the slide back using a block of wood and a hammer, or sometimes you can just smack the butt of the gun while holding the slide and it'll knock it loose. It seems to happen no matter what ammo I use. Is there anything to polish or grind that can fix this? I occasionaly had the same problem with an M9A1 and an old M40. I'm starting to lose faith in these guns.