I used 19.0 grs. of 4198 with an RCBS CSA 300 mold.

I think I might try loading smokeless in this rifle.  I am trying to get a handle on the original black powder ballistics were for the cartridge.  This time Wiki is no help. Doing a little searching and I found one reference to an original factory load using a 265 grain bullet at 1400 fps.
   The vintage Winchester mold I have with its handle stamped 40-82 produces just that very bullet a 265gn fn-pb.
   The only comparable cartridge I can think of for load data is the 401 WSL at 1.5" case length. The 401 works at a way higher pressure than I would ever want to put through a BP roller so no real help there.  No doubt I will figure something out but I would like to be sure that 1400 fps with a 265gn bullet what I should be looking to duplicate with a smokeless load.  Was that the original BP velocity and bullet weight ?

I tried 21 gn of Accurate LT-30 and velocities were hovering around 1300 fps. I used pistol primers as an earlier pressure indicator and they showed no sign of high enough pressure to flatten the primers.  The edges were still rounded . Even with the large diameter firing pin no primer cup material was cratering around the firing pin. I didn't shoot groups but at 100 yards an 18" steel gong was no challenge. 
  I like the load. Its easy on the rifle and the brass and about comparable to a 44 mag load fired from a revolver.

Late yesterday too late to shoot I cast some bullets from an old Lyman mold # 412263 . Its a round nose plain base bullet running about 300 grain in a soft alloy.
  Its kind of an odd two diameter design having two wide drive bands at the base with one wide lube groove between those then forward it drops nearly .002" diameter and has another two wide lube grooves with one very narrow drive band between.
With this bullet with just the bottom lube groove filled it can be seated long with just enough bullet in the case to cover the lube groove.  I found that with this bullet and shallow seating this rifle will then chamber a cartridge with the bullet sized to .410"
   I have a few so loaded to try today. I reduced the 21gn LT-30 I used for the 265gn bullet by one grain to compensate for the increased bullet weight. If the rifle likes this bullet it should be about perfect for general use. I do like the old Winchester 265gn bullet for GP use. 
  I was reading something about a model of rifle called the hunters rifle originally offered in 40-50 SS. It was a shorter lighter weight model for deer hunting. That describes my rifle pretty well. I see it as not a long range rifle but as a short range hunting rifle having all the capability of a 44 magnum revolver but much easier to place shots precisely. 
  I think I might try it for eliminating some gophers on our property. They are driving our dogs nuts and the dogs are digging tunnels to China.