Gasgunner, If you want to go really weird, but with historical precedent, I have a Niedner rifle (44 1/2 action) with a .23 caliber barrel, the cartridge being a necked .28 - 30 case. It happens that Michael Petrov has some tooling for that cartridge, so I sent it up to him, and he has shot it a bit. I don't know if that small increase would clean up your bore and chamber problems.
Personally, I'd be more inclined to go with a rebore to something like .2 - 35 or any of the .25 cartridges mentioned above. However, since Niedner was a wildcatter, maybe you should consider making it into something like .25 Hornet just to keep his spirit happy.
The action in your rifle is NOT a Hauck. I have one in my safe and could take snap shots if anyone wants to see it. There are similarities, but the differences have been pointed out by others. Hauck is much bulkier - I used to own one with an Elmer Herman .45 slug gun barrel (chambered to .45 - 70) whose proportions looked about right. The barrel must have been 1.5" diameter or greater. It may have been stocked by Shelhamer - at least I thought that at the time. I sold it about 35 years ago, so can't check my memory.
