I picked this up last month. I tried a #10 Cap Primer, but it seems too small (won't fire the gun, although the cap ignited after sever tries.). I figure someone here would know what size caps I need to order for this.
Thanks.

Updated: a #11 worked.

__________________
Watch & Pray

Right offhand, I would say you need some 4 wing musket caps. They are larger than a #10 percussion cap.

There are also #11 percussion caps. Some of my revolvers prefer 10's some prefer 11's. Musket caps are very large comparatively, but now are available with wings and without.

Make sure your nipple isn't clogged. A nipple pick is usually built in the "T" style wrenches. A straightened out paper clip will do in a pinch, Just avoid anything a magnet can pick up as it could spark and be more interesting than you bargained for!

Ivan

Cqps are not all alike. I've used #10 caps on those guns - as long as it fits on the nipple and goes down all the way it will be fine. A larger cap can be pinched a bit to keep it from falling off. Since we cannot see the top of the nipple, I would not be surprised to find the nipple has been peened-over by dry firing. The top of the nipple should be flat and even, not mashed over with only a smallish hole left for the fire to get through.

Dry firing is the bane of percussion cap guns. NEVER do it.

The #10 basically didn't seat all the way down.

Maybe I'll order some #11's. I cleaned this out before attempting to fire it. I really just want to shoot it once to see it work.

__________________
Watch & Pray

I'd try #11s. If they are too large for the nipple, you can squeeze them a little so they can be forced on the nipple. I use #11s for everything. Musket caps are too big for anything other than muskets and some larger rifles. I have a Sharps replica and a 3-band Enfield which use musket caps.

If you already have some #10's and you just want to shoot the pistol a few times,,I'd simply remove the nipple and trim the dia down a bit so the #10 will fit correctly. It doesn't take much, just keep a slight taper to the nipple as it originally has.

Ordering a single lot of #11's just for a few shots here can be kind of expensive. Maybe you have other uses for the 11's though.

One other thing I see is that the hammer doesn't appear to be striking the nipple squarely.
That's just an observation based on the angle of the nipple and that of the face of the hammer.

The hammer is counterbored to catch cap fragments and maybe the counterbore is more correctly matching the nipple face. But in the pic, it appears the hammer striking the nipple at the rear edge of it.

That angle (along with the poor fit of the cap) isn't going to get you much positive ignition.

Correcting the angle of the hammer to the nipple to better the contact means bending the hammer in this instance,,or carefully recutting the counterbore in the face of the hammer to better match the nipple.
You can't do much with the angle of the nipple itself as it's a tang breech,,not a drum breech.
The latter you could turn a few degrees to match up better.

You might not get a perfect match between the two surfaces, but the closer they meet flat the better to smash and ignite that cap.

When you have the nipple out to trim the stem down to #10, clean up any battering from dry firing all ready mentioned and make sure the flash hole is clear in it and the breech plug

"Musket caps are very large comparatively, but now are available with wings and without."

The wingless caps are no longer in production. A lot of the members of the North-South Skirmish Association liked the wingless caps, but alas, they are no more, unless you have a stash of them.

__________________
John 3:16
WAR EAGLE!

#11s are probably your answer, BUT... before you go buy some, examine the nipple closely to see if the top has been slightly "mushroomed" by dry firing. If so, remove the nipple, chuck the threaded shank in to a hand drill, rotate it at slow speed and hold a flat file to it, just enough to reduce the mushroomed area to original diameter.

BTW, I hear Lincoln will be at Ford's Theater the evening of April 14...

__________________
Pisgah

Looks like an old CVA derringer kit gun. Probably ran about $39 at the time.

Thanks for all the info.

I cleaned-up the nipple. Tried a 10 again and it really doesn't fit unless I force it. I'll find some 11's eventually.

__________________
Watch & Pray

"BTW, I hear Lincoln will be at Ford's Theater the evening of April 14..."

Aside from that Mrs. Lincoln, did you enjoy the play?

I owned one of these years ago, and I used #11 caps.

This was back in my younger and wilder days. My friend Kip (who built it from a kit and then traded it to me) and I took a 1/2" drill and bored it out to .50 caliber. It really wasn't any less accurate after the conversion. Safe? Probably not. Fun? Yes. We traded it back and forth a couple more times until we lost the desire to fool around with black powder.

CVA percussion Derringer uses a #11. If it won't slide down and seat the nipple has been mushroomed and should be replaced with the right size and thread nipple. If a #11 is ever so slightly loose a light pinch will snug it up and hold it in place. Don't trust half cock for a safety and carry it around with a nipple in place while doing so. Yes gamblers used to do it but it's not a good practice.

Finally shot it. The #11 worked.

__________________
Watch & Pray