Greetings! I am looking for information regarding the cleaning out of what appears to be a clogged flash hole on a friends .45 cal Thompson Center Hawken. The first thing was the clean-out screw itself was all bunged up, so I had to remove the head, drill out the rest and re-tapped the hole for an 8-32 allen set screw. I have removed the nipple, which I am also replacing. But I need advice on the diameter of the flash hole in the barrel itself. I cant seem to find it! I mean there is a pretty large diameter (.08ish) partial hole, but it does not go all the way to the bore. I can't see down in there too well with a borelight, and I've probed around with a real small drill bit (.020ish), just to determine if there is caked residue clogging the passage, but I have not found much in the way of clues as to just how the "Bang" from the percussion cap is supposed to get to the powder in the barrel! What diameter hole should be in the barrel wall? Would it be the size that is at the base of the nipple? I have worked on a lot of firearms, but I must admit my ignorance when it comes to Black Powder. I would really appreciate any sage and wise advice in this endeavor!