Using a drill bit is not needed, and could damage things! Pull the nipple and let it soak it a little solvent and it sould soften it up enough too use a pick on it.
The only time I had a similar incident it happened in the field after about 15-20 shots on a hot humid morning. I was using a sub. :shake: for powder, 1st mistake, 2nd mistake my wiping method.
Let me explain! I only used a sub twice in my life the first two times I ever shot. The first time was the incident I just related and the second was after I changed my wiping practices.
:nono: When you wipe between shots if you take and go all the way to bottom with first patch you push all the crud to the bottom of breech and that is exactly what I did the first time out. After the 15-20 shots the crud that didn't come out on the patch was pushed into the breech flash channel and eventually out into the nipple blocking the nipple solid. That's when I had my repeated missfire.
After reading a post on this forum I changed my wiping practices I still run a patch between shots but, with my first stroke I only take it about 2/3 of the way down the barrel. At this point I either pull patch on jag and flip over using clean side or merely grab another patch and finish cleaning all the way to bottom of barrel. This way I am picking up more of the crud and not forcing it back into the breech channel and altimatley the nipple. This helped immensely but, I still was getting a large amount of fouling. The change in wiping had stopped it from getting so bad that it eventually blocked the nipple.
The second thing I did was to change to GEOX black powder. Once I tried it I never looked back. :blah:
The third thing I did was even a greater improvement and that was I changed lube. I now use Hoppies #9 BP and Lube solvent. I have shot as many as 20 shots out of curosity without wiping between shots and never had a problem with fouling or had accuracy suffer. :shocked2: Nowdays I usually will wipe between shots if I plan on shooting much or target shooting and I always use GEOX BP, and Hoppies #9BP& S is my choice of lube!!!!!!