I just completed my project SAM commander frame. I tried mating it with my Norinco Commander top end. The slide doesn'st want to go in, so I lap it with the frame no problem. but when I tried finally installing the complete slide assembly, it would not slide back freely when I will try to pull the slide back. as if something is obstructing the barrel or the slide. Is it the upper/lower lugs, barrel link etc.? could you please help me. totally confused, any tips, it will be apprciated. thank you