You might just stripped something or you got a jam... Don`t use cheap bbs they look cheap but in the future it will run you up more cash, the only bbs I would buy if I totally need it fast is the Crosman NEW Heavy .25 the black ones, they won`t jam but you will loose lots of accuracy comparing to BBasterds or other higher brand bbs, I`ve heard that The new crosman .25s are G&G bb quality (NOT SURE)
