The problem you are having is that the gun you have was built in .53 cal. but marked .54 cal.. I owned one of the one in one thousand models with a serial #less than 200. I got it cheap because the owner, had won it at a rendezvous, and couldn't make it shoot, and had a hard time loading it. A little research disclosed the problem. I bought a .520 RB. mold, and the problems were solved. These guns actually shoot very well, and can usually be bought cheap, because everyone tries to shoot .530 balls in them.
Hungry Horse