In the Marlin barrel Lyman recommends velocity be kept to 1600 FPS for accuracy. Try 36.0 grains of 5744 for the 405 cast bullet. The only 405 grain cast load that I have used a lot is 13.5 grains of Unique with a federal Large rifle Magnum primer. This is a great practice and plinking load and requires no fillers or wads. This will yield 1100-1150 fps from my 22 inch barrels. Its accurate and uniform although on paper its not a likely sounding load. RE-7 is a good powder for the 45-70. For black bear or moose, the 350n grain Hornady RN is perfect at 1800 fps.

As of late I have been playing around with the 500 Grain Government RN Montana Precision cast bullet. I have loaded it to 1250 fps with both 5744 and Goex 2F. I love the NEF rifles for black powder because one screw and off comes the barrel for cleaning. I shoot the 22 inch Handi rifle and the 32 inch Buffalo Classic.