Doesn't the Marlin .44 mag lever rifle still have micro groove rifling ? If so it may have very poor accuracy with any cast bullet!
Funny, "Everybody" knows you can't shoot cast bullets in Micro-grove rifleing. Everybody, that is, except those of us that actuallydo it. Wth Microgrove or multigroove rifleing, the most important thing is bullet diameter. Bullets need to be at least .001 or even .002 OVER groove diameter. IME, slightly softer bullets do better than very hard bullets. Use a good lube, or combination of lubes,like the Lee liquid alox over other lubes as mentioned in the earlier post. Just be SURE your bullet diameter is large enough.