Playing with fixes like that is fine and dandy, but if you're shooting smokeless, you can shoot a lot cleaner by shooting a 250gr bullet. Not sure what you're shooting now, but probably lighter if it is getting that dirty. That and a fast powder and good crimp. I shot lots of 45 Colt through my '73 Trapper, but getting that tenth round in and then lined up straight on the carrier was a hassle. So I switched to 45 Schofield rounds. Both with 250 gr bullets. I go a few matches between cleaning and that is Qtips with ballistol inside the carrier, and down the sides and corners of the mortice (opening) top and bottom. I haven't taken the carrier out to clean it thoroughly in years.
Your POI shouldn't change much at 25 yds. Rifles don't recoil much, especially a Henry, so lighter vs. heavier bullets don't change elevation much at short distance. Pistols a different matter. Anyway just another possibility. More than one way to skin a cat. Some ways the cat scratches you less.
Now if you want to shoot BP in that Henry, by all means convert some 44 cases. Mine runs pretty dirty even with the heavy bullet with BP. So I just don't shoot black in that rifle. It is becoming my Wild Bunch gun. I have other calibers more suited for smoke.