I'm using the LEE 330 grain RNFP cast from wheelweights, a milk carton card, 55 grains of Swiss # 4 (1,5 Fg) blackpowder. Federal Large Rifle Magnum primers.
Swiss # 3 (2 Fg) will also work. Swiss burns cleaner and has a little more "Oomph" compared to other brands.
Special considerations: Copper-plated bullets have no lube, so I'd expect precision to decline rapidly with blackpowder, unless You swab the bore between shots. You might benefit from adding a "grease-cookie" between bullet and powder. You'll also need a card wad over and under the grease-cookie.
If You decide to experiment with reduced blackpowder-loads it is imperative to fill the void between bullet and powder with card wads / cork wads or something similar, or a ringed chamber may be the result.