I have a 50 cal CVA Mountain Stalker and the only time I had ignition trouble is when I tried the 777 powder. Pyrodex was fine and I found that the Goex brand of real black powder worked the best for me. 85g of 777 is equal to 100 grains of Pyrodex or Goex if you are measuring by volume. As was mentioned before that is a very stout load. I get my best accuracy with a .490 ball, .015 patch and 85g of Goex. Once you get the ignition problem solved and get a tighter patch for the .490 ball try shooting 5 shot groups while varying the powder charge up and down in 5g increments. You will find a "sweet spot" where you get your best groups.

Getting there is half the fun,

Bob