Are you talking about this one?
They are an interesting little gun but IMO, not quite up to a target pistol.
The grip is much too small to give a good steady hold like a real target pistol needs.
It does replicate an actual gun made by Allen & Thurber in the late 1840-1850's time period
The orignals were made in .34, .41 and .45 caliber.
The Hoppes's reproduction has one fault which I corrected on mine.
The flame channel from the bottom of the percussion nipple goes crossways from the right side of the gun to the left. The left end is threaded and one of the screws that holds the side panel in place uses that hole.
That is not the problem. I mentioned it because it might give you a better understanding of what is next.
My gun would pop the cap but misfire more often than not.
After studying the bottom of the bore I noticed a very tiny little hole that was drilled into the crossways flame channel.
Going to the local hardware store I managed to buy a 12 inch long, 1/8" diameter "aircraft length" drill.
Drilling that tiny little hole out with the aircraft length drill solved the ignition problem.
(Warning. There is a very small amount of material around that crossways flame channel and if you drill all the way thru it into the area where the lock tumbler and mainspring are, you ruined the gun.
Anyways, the only other strange thing about these guns is they do not use a standard percussion nipple.
They have a very short nipple with a flange on it.
I seem to recall seeing some of these special nipples for sale at Track of the Wolf.
Hope this answers some of your questions.