Forgive me for being a slow to the party. I’ve been traveling for work. I wanted to add a few comments for the benefit of new builders.
Vents on old many old guns were drilled for proofing before the guns were built. We know that to be the case. And many barrels were made by people other than the gun builder. Vents were drilled before locks were inlet. So, we might expect some variation in placement of vents in such firearms, especially American-built firearms. And that’s even before considering variation in the skill levels of builders who constructed those antiques. In comparison, if we look at high-end English firearms, such as later period shotguns, we’re generally looking at every part being built in a coordinated effort, with careful planning and precision —and lot of guns with vents at sunset position. The point of my mentioning this is to note (for the benefit of newer builders) that the question of where vents occurred on various old guns is a bit distinct from a discussion about where a modern builder may want to put a vent if he/she is drilling the hole after the lock is installed.
Regarding how much powder to use, I think a lot of us would suggest a good answer would be “enough”. There also seems to be such a thing as “too much”. Most of us try to keep the vent clear of powder (so as to avoid the “wick” effect). For similar reason, most of us also try to avoid piling a thick layer of powder over the vent. But there are pros and cons to keeping the vent completely uncovered, verses having a light covering. I generally try to avoid covering the vent, but I charge and prime from a single horn, and if I spill a little too much powder in the pan and it slightly covers the vent, I don’t try to correct it. It works both ways. I’m shooting a rifle that is ignited by a rock. I’m not surprised or disappointed or frustrated if I experience some mild variation in results—the same sort of variation that the old guys dealt with. For me, it’s part of the fun. I like a nice crisp “boom”, but if once in a while I hear “ka-boom”, no big deal. If I want or need complete predictability, I’ll pull something else off the rack.
Regarding Pletch’s experiments, I like seeing them. But I’d like to see more control of variables. “Banking” this way or that seems a bit vague to me. Is he covering the vent? If so, by how much? How thick a layer? Where is the point of diminishing returns? (If he described those details somewhere, then I missed seeing them. You can point me toward more information.)
I liked Rick’s observation about vent picks. I almost always push a wire pick through the vent and into the center of the main charge before priming the pan. This is a round-wire pick that is no larger in diameter than the vent hole itself. I learned that from a mentor who was a two-time national champion. It works well for me. And sunset position works well with that technique.
I also liked Smylee's observation about pick design. I NEVER use a pick that has any risk of reaming out the hole. Picks are pushing tools. They are not digging tools. They should push powder and fouling out of the hole without damaging it. A careful review of Madison Grant's book on pouches will show you a half dozen or so antique picks. All of them look to be thin wire.
