MIke: WADR, CLEAN the lock, frizzen, and flint, as well as the barrel between shots. I don't really know what you are referring to about using a " double charge" in the priming pan, unless you are using one of the mechnical priming tools that dispenses 2-3 grain of 4f powder when you push it into the pan. If you have been reading this forum at all, you should understand that you are better off priming with the same powder you put down the barrel, and you can- and should- leave that priming horn at home! Its just something else to lose in the field! In pistol locks, one push of that lever and the 2-3 grains of 4f powder it dispenses if often enough. Not so with most rifles. Humor yourself, and use 3 or for charges of that prime. Do use a pick to clear the vent before priming the pan. Every time you load.
If you don't clean your pan, with a cleaning patch, so its shiny again, and you don't wipe the flint, frizzen, and cock, and the barrel around the vent, that residue of powder will attract moisture, and it will ruin your priming powder very quickly. I was hunting in the rain in Eastern Tennessee on Labor Day back in the 80s, and failed to wipe the underside of my flint. I dried everything else every 15 minutes, but I forgot that moisure can collect on the underside, too. Well, when I fired my first shot at a wild boar, the frizzen sparked, and the water from the bottom of the flint put the sparks out before they made it to the pan. Left a wet line on the face of the frizzen to brazenly tell me how I had screwed the pooch! I have not made the same mistake again.