Major and Flint,
I currently have 4 Henry rifles. Two have been converted to side load Henry Transitional's. The other two are standard front load Henrys. I modified the front load Henrys some years ago with just such a cartridge stop screw suggested by Major. It works a treat. Oh, all my rifles are .45s, and I currently shoot Cowboy 45 Special brass. I started out cutting .45 Schofield brass to that length. It almost perfectly duplicates the old .44 Henry flat load. I can load 18 of 'em.
The two rifles I have converted to side load transitional use a custom Carrier Block with a spring loaded stop and a loading slot cut into the side. The 24 inch rifle will hold 18 and the 16inch trapper will hold 12. These guns are capitol FUN.
I also shoot a '66 rifle, 44 Spl, cut to 16 inch Trapper length, in which I shoot Russian cases. A real close approximation of the .44 Henry Flat as well.
With All of the above, I partner either Cap Guns (.44s) or appropriately chambered Open Tops. I really like partnering the .44 Open Tops as that was almost the exclusive chambering of the Open Top.
The short cartridges in ALL all of these guns are just superb. About as close to what was as we can get. I'm always saddened we cant get .44 Henry Flat ammunition so we could play with the originals.
Coffinmaker