KSC Glock 23 Magazine Butt-Cap
 

the damn thing is stuck, can't get it to move. I have no idea why, I'm wondering if this is a common problem and if theres something I can do to get it to come off smoothly.

Ok well did it move before or did you just get the gun and cant move it. if you just got the gun then if you look where the bbs go at the bottom theres a little lever pull it towards the top of the mag and slide the plate.