As has been stated, it is a primer adapter for a percussion firearm. Thank you to the two brothers who pointed out that these were mentioned in Ned Roberts' book, The Muzzle-Loading Cap Lock Rifle. This book was first published before World War II, so the idea is not new. Primer adapters are probably older than a lot of the mass-produced "traditional" rifle designs people are shooting now.
I am not trying to sell anybody on primer adapters. Percussion caps will remain my first "go to" as an ignition source for percussion guns. I think percussion caps are probably more practical... You just push one onto the nipple. With the primer adapters, you are not only handling a tiny little primer, but you are also manipulating a separate cap that houses the firing pin, and has to be screwed off and back on for every shot. This equates to extra steps in loading and extra parts to lose. With the adapters that use rifle/pistol primers, I have wondered if it might be possible to put the primer in upside down. That would not happen with a percussion cap.
However, it is good to know what your options are, so those options can be utilized in times of shortage. If you can't get caps but can get primers, an adapter can keep you shooting. As for the flintlock versus percussion angle, I own and enjoy shooting both. It's not really an either/or proposition.
A lot of people will tell you that you can pick up a rock and put it in your flinter and keep shooting. I wonder how many have actually done this. In the old days, traders sold an awful lot of flints to their Indian customers, who were the original American flint knappers and evidently felt that a half dozen flints were worth a deerskin. There have been debates about bevel up or bevel down, or French versus black English flints, and articles have been written about how to select flints for your gun. I just don't subscribe to the "any old rock" theory.
I understand that some primers may be hotter than percussion caps, which suggests that if you have to shoot black powder substitutes, you may have fewer hangfires and failures to fire with primers. Some have suggested that primers are more consistent than caps, and for precision target shooters, this may be something to consider.
I have a relatively new custom rifle, a beautiful Hawken, that blew the hammer back to full cock every time it was fired. The nipple was new, with a small flash hole, and the mainspring is good and strong. There is no reasonable explanation for this blowback. I changed the #11 nipple out for an old one sized for #12 caps (I have stash of these, both nipples and caps), and enjoyed positive ignition and no blowback, but had to use needle-nose pliers to get the spent cap off the nipple, which was a pain. My Alcan #12 caps are around 60 years old. Old caps were made with thicker, stronger walls than the new ones, and they stay on the nipple very well, but this can also make them harder to remove after the shot.
Anyway, I bought a Mag-Spark 209 adapter for this rifle but haven't had a chance to try it yet. One of the hold-ups was that 209 primers were unavailable, and I've discovered that not all of the 209's out there will fit the Mag-Spark. I joined the Modern Muzzleloadfing Forum (under a different alias) specifically to ask about this. One fellow posted results of pretty extensive measurement and testing, and found that some of the more widely available 209 primers just would not work at all, and even some of the better known, name brand primers didn't all fit. The consensus was that Federal 209 primers were the most consistent fit, and I finally found some of these. Still haven't had a chance to try the adapter or primers, but I will. I also fully expect to lose the adapter's cap, so I ordered a spare.
In any event, primer adapters for percussion guns have a place in the traditional muzzleloading world, and I would not put anybody down for trying one. If you get one, it would probably be a good idea to try your primers in the adapter before you go to the range, to make sure they will fit, and separate the ones that won't fit from the ones that will.
Best regards,
Notchy Bob
