I have had this gun for several years and have only put 200 rounds or so through it. I have never cleaned it because I can't get the damn slide off. I have read the instructions, watched eBay videos, you name it... I pull the slide stop all the way out, push the watchmacallit down in the mag well, etc.. The slide just refuses to come forward and off. I can only get it to move maybe a half inch. Any suggestions?