actually before u do that, i just remembered my classic arms new orleans ace pistol. When i built the thing, i couldnt get it to fire off the cap, i used to have to back the nipple out 2 or 3 turns and then it would go off. Try unscrewing your "nipple" 2 or 3 turns and see if it will go off with 1 cap. dont load it, just put the cap on and test it. Some nipples are to short and dont let the hammer hit them all the way.