I acquired a ML shotgun about 40 yrs ago & have hunted with it quite a bit over the years. There are two secrets to one going off with Black Powder when the cap fires. 1st is that the channel is clear & the cap flame actually gets to the charge. 2nd is that the powder is dry. Many tell you to snap a cap on the niple to blow out the passage before loading, I "Never" do this as I don't want to take the chance of cap residue plugging it up. When I know I'm going to take it out hunting the night before I swab all the oil out of the bore with alcohol or acetone, then set the bbls muzzles down to drain. If I decide to shoot it without prior planning I use a patch & swab as best as I can, then load & shoot a full charge without letting it set. This will normally burn off any remaining oil. In either case as swabing I simply make sure air is blowing through the nipple. "If" a black powder gun fails to fire either the flame didn't get to the powder or the powder was wet. Some of the Subs are harder to ignite & require hotter caps. After about 2 misfires I figured out what the problems were & have had no trouble since.
