Rover,
The throats on my Rugers are .430 and the barrels are .429. The same goes for for my rifle.
I use .430 coated .44 Magnum bullets in both revolvers and rifles.
Your rifle being of older design (The firing pin extension on the older models was retained w/ a cross pin) may have a .427 bore.
New
Old
I use several different ones. That is what I'm using right now with a 1/4 tsp. of Lemishine a little squirt of Dawn dish liquid and pins.
I get the best results with no more that 250 .44-40 cases and a full tank of water in the Frankford tumbler.
These are awesome. I took mine apart when I got it home to smooth out and polish some of the internals and just put it back together. It was already so smooth inside there was no room for improvement. It has been a real shooter for Wild Bunch.
I had my ammo stored in a plastic bin in the back of the truck for EOT when it was held in Indiana. I had smokeless ammo for side matches and black powder ammo for the main match. It had rained several days before the match and my tonneau cover leaked funneling all the water into the ammo bin. all the ammo was sitting in about 3" of water. As luck would have it I live about an hour away so I went home and got new main match ammo. The wet ammo I took home and tried shooting it and all the samples of black powder ammo and shotgun ammo shot fine but the smokeless ammo was horrible. I ended up shooting all the black powder ammo at monthly matches without any problems but the smokeless ammo even after trying to dry them out in a case dryer for days were a no go. When I pulled the bullets some of them actually had water pour out of them.