All of the above is good advice you may also want to check that your nipple is not battered or to big for the caps you are using, especially if you have some of those Dixie caps or some chinese caps. If the nipple is to big for the caps you can either get some bigger caps or pad the threads and hold it in the Chuck of a 3/8 inch drill motor while it spinning take a file and turn it down slowly and carefully until the cap will just set against the prim in its top when it is squeezed on. Lee