It's funny how many people go out of their way to chime into a black-powder defense thread about how much better modern options are.... It's like someone asking questions about rimfires and someone else comes along declaring how wonderful .357 magnum is. I read your posts and see that you have plenty of firearms experience. Also, I have many cartridge-firing guns that are my primary go-to's for defense, but as someone already said, my blackpowder guns are certainly not the
last guns I'd reach for... I don't have any larger than .44, but the .61/20 gauge seems awesome for the OP's criteria!
anyhoo, I've read this whole thread (took me a while) and there have been some worthwhile posts here and there
. When my black powder guns are clean, they are loaded. I don't get to shoot them as often as I'd like, as the indoor range I'm a member-with does not allow black powder shooting. Mine have gone several months between shoots more often than not. Also my two 1851's and 1847 have each spent a year+ loaded in the safe, with the anti-moisture packets, (each at a different point in time) before firing, just to see how it goes after all that time. After the year+ tests, I remember at least one shot delayed by a half-second or so, but that is the only problem to report. Granted I do not live in a Marina, but I'm not far from the coast, close enough to smell it. The luxury of a boat, is you can go a couple miles out, and shoot without bothering anyone! (Not sure on the legalities...) If you have the gas, you can always pull a monthly or bi-monthly "Bill Hickok" check.
The nail-polish suggestion sounds like it could only help. Not sure if anyone mentioned this yet, if not this can be considered the most important part of my post: Keeping the NIPPLES CLEAN is possibly one of most important parts of reliable ignition (just my opinion, could easily be proven wrong by wet powder but anyway). If you are going to trust your life to your percussion gun(s) don't forget to fire caps on the empty gun after you clean it, if anything fire TWO caps on the empty gun(s) after you clean 'em before you load 'em. Nipple-picks are your friend. The only times I've had failures to fire with my percussion guns, were when I was too busy, too lazy or too miserly to do this! Whoever posted the photo of the magnets on the side of the gun with extra caps is brilliant!!! In the event of a misfire, another advantage of a single or double bbl percussion gun, is you don't need to turn a cylinder to recap and retry, you can just pull the hammer back and throw another cap on without risking blowing your hand off (keep pointed in safe direction of course).
I LOVE my single-shot percussion gun, now this thread has me itching for a Howda, and double .44!!!