I'm sorry I can't cite chapter and verse, but I have seen these "feather holes" and I read some about these in the past. I think the first reference I saw was in an article by Harry Merklee in Muzzle Blasts, maybe in the mid to late sixties. I believe he said blue jay feathers were preferred but I don't recall why.
In any event, while it may be splitting hairs, the feather was not used as a vent pick but as a vent plug, to keep powder from filling the vent and leaking out during loading. I suspect a feather quill from a small bird would be ideal as a vent plug... Tapered on the end, nonabrasive, flexible, compressible, and readily available. I'm sure the flintlock shooters in the crowd will agree that it's best to have the vent open, so the main charge detonates from the incandescent flash of the priming. If the vent is full of powder, you essentially have a fuse, resulting in a slight hangfire.
However, I've lately seen several references in old literature to "self priming" flintlocks. Obviously, this refers to a vent large enough to leak powder from the main charge into the pan. While it may surprise some of us modern folk, this was actually considered an advantage to some people in the military and on the frontier, because it eliminated the need to prime as a separate step in loading. John Palliser specifically recommended a "self priming flintlock" for running buffalo, and Berkeley R Lewis mentioned it in his book about American military small arms. I've seen a couple of other references I regrettably can't recall at the moment. For both of these references, note that really accurate fire was not necessary. Buffalo were shot from horseback at point blank range, and military muskets were fired in volleys. Hangfires would not have been much of a problem. I am aware that some of the old "manuals of arms" for military muskets called for tearing the paper cartridge open and priming and closing the pan before loading, but Lewis did mention self-priming flintlocks in the military context, so I mention it here.
I have a hypothesis that the ability of some flintlock guns to self-prime may be the reason the northern natives held on to their flintlock Northwest guns so far into the percussion era... If a flintlock gun primes itself during loading, you don't have to handle percussion caps in freezing weather, with gloves on or with cold hands. The other thing is a large vent is less likely to get clogged. I have experienced a few misfires with percussion guns, attributed to a clog in that tiny flash hole in the base of the nipple. I suspect I'm not alone in this respect. I have found that a well-built flintlock, even with a plain, bored touch hole, is just as reliable as a percussion gun, provided the shooter takes the trouble to maintain it.
Anyway, getting back to the original topic, those very large vents we frequently see in original flintlock firearms may not necessarily be burned out. They may have been made big for a reason. If you close the pan and the vent leaks powder, you have a self priming flintlock, which saves a step in loading but may result in a hangfire. If you don't want the pan primed during loading, either for safety or just to keep the vent clear, you plug the vent with a feather, which you pull out later and then prime the pan in the "conventional" way.
Best regards,
Crooked River Bob
