New to black powder. Just picked up a 32 cal., percussion cap, Dixie Gun Works, made in Japan around the mid '80's. Using Goexx 3f, 25 to 35 grains. I'm using a dry cleaning swab between shots, shooting a 310 ball with a dry pillow ticking patch. After 12 to 15 shots, I'm getting a failure to ignite. Could it be a worn nipple? Any help would be appreciated.