over powder wadding?

As long as your loading density is over 35-40% you should still get decent ignition standard LR primers without fillers/wads, though Lyman does use them.

If you are having ignition issues without them (and pointing the muzzle straight up after chambering the round will cure it to determine that position sensitivity is the actual cause) then I would use a bit of dacron fiber - pillow stuffing - to keep the powder in place. Dacron will work for both straightwall and bottleneck cases and is often used these days as it is versatile, easy to handle, and creates no mess. Cream of Wheat and cornmeal are often used traditionally as fillers in straightwall cases, as are commercially made cardboard/fiber wads or homemade wads punched out with a sharpened case from meat tray foam. You have to be aware when using fillers that they effectively reduce case capacity and change the pressure curve to that of a smaller case. Not a real big problem necessarily with a reduced cast load, but still something to be aware of and keep an eye on the primers for pressure signs.

Do a search next door at Cast Boolits for different fillers. You will find a lot of different kinds and often explanations why one or another is particularly good in a specific situation, and also some load info, too.

I might be looking for something slower than 4198, but there's no reason not to see if any of your rifles prefer it. (I have had good results with 3031 & RL7 in .45-70 cast loads.) According to my Lyman CBH, you are way below starting loads for .45-70 at 25-28gr and .50-70 loads start in the 26gr range.

.45-70 IMR4198
366gr cast bullet START 41.5gr with dacron wad, 50.5gr (no wad) MAX
451gr cast bullet START 33.0gr with dacron wad, 43.0gr (no wad) MAX

.50-70 IMR4198
334gr cast bullet START 26.5gr with dacron wad, 34.5gr with dacron wad MAX
440gr cast bullet START 26.0gr with dacron wad, 31.0gr with dacron wad MAX

I don't have any data on hand for the .43Mauser, but I bet you'll find that on CB, too.