A few questions.. how old is the nipple on that rifle? When you get ready to shoot do you swab the oil and stuff out of the barrel before shooting? What do you use to swab the bore of the rifle with.. I find I have better luck with pure alcohol when I swab, and then make sure that you run at least two dry patches down the bore to make sure that barrel is dry.

Last question.. what caps are you shooting? Next time out, start with 70 grains of powder and work from there. Also keep the sights tight...use some lock tight in the threads if you have to.