Just bought my first Glock and i'm probably the only guy who has problems re-assembling after a field strip. After i put the slide back onto the rails and slide it back, the take-down slidelock moves back down and the slide doesn't lock -- i have to do it over and over before it works right; can anybody help? Also, is it normal for there to be a bit of a gap between the slide and the frame. Sorry if this is a stupid question, but i want to make sure i'm not damaging the gun when i re-assemble.. Thanks very much for any help here.