FJ,
The Armory 44 Chambering would chamber the 44 Martin, the 44 S & W Russian, and the 44 Remington. The 46 RF chambering also accepted the 44 RF. This come from pages 61 and 62 in Bruce McDowell's book, and I have found also that the 46 RF also chambers 44 Rem./Colt C.F.
The longer 46 Rf carbine cartridge was used in the 46 R.F. was also used in the 46 R.F.factory and non factory conversions.
I have An Armory 46 RF conversion (later converted to C.F.) here that I'm making a recoil plate for and the cylinder will chamber 44 Rem/Colt C.F. and 44 Rem. Mag brass.(the latter being almost a perfect fit due to the larger Rim dia. I believe it to be the same Dia as the old 46 RF, if not Dead on, then mightily close). The 44 Rem/Colt (44 Colt brass)chambers fine and doesn't wobble in the chamber, but the rim dia is smaller.
The first 1873 Remingtons were chambered in the 44 Rem/Colt C.F.
My Armory conversion in 44 Rem. is s/n between the two pictured on page 63 of McDowell's book. Mine is of the type of the top picture.