(Photo courtesy of DJR)
FWIW I have the MowreyPlains Rifle in 50cal with all brass hardware, including the forend and I love it! They are a modernized copy of the Allen & Thurber design. I bought mine used for $60 ... "broken - as is" ... as the screw securing the hammer was broken off inside the tumbler. I called Mowrey for a new hammer and tumbler and they just sent me the replacement parts for free, but that was a looooong time agonow.
The one I have is IDENTICAL to DJR's rifleshown, down to the all brass hardware, rear semi-Scheutzen style buttstock and all, but mine wears a factory target blade rear sight. These were made for roundball shooting and have a 1-in-66" twist rifling which I believe is only 0.012" deep. I use 0.490 RB with 70grs FFFg and dry-lubed 0.010" strip patches cut at the muzzle.