I recently purchased my first Glock 17. It was a police trade in from the mid 90s, I've had it on the range a bunch of times and it's worked flawlessly so far. So I've been doing a lot of dry fire practice with snap caps. The other night I had an A-Zoom snap cap stop the slide short of battery. I smack the rear of the slide with the back of my hand, and it goes into battery. Trigger and all work like they should. When I attempt to rack the slide it's locked up tight. I couldn't budge the slide. Stripped it off, took it apart, and ended up beating the snap cap out of the barrel with a dowel. My question is are AZoom snap caps that out of spec, or is this an indicator about something else I should be looking for?