I have the BD-XR and have put a lot of different stuff through it. If I were going after elk, I might be loading 120 grains of loose Pyrodex RS and a 250 grain T/C Shockwave. I am shooting some fantastic groups with that load. I would start my rifle out at 100 grains and work up. My rifle does not seem to like anything over 120 grains of loose powder.
Another load I shoot but not for elk is the T/C 240 grain .44 caliber XTPs. I was shooting fantastic groups with 100 grains of powder at the 50 yard line. In fact the first two shots looked like one, dead center in the bull. The third clover leafed. Why, I have not figured out, but at 100 yards they opened to a 1.5-2" group and a few inches high....

I have not figured that out yet.
You might want to try some big conicals out of the Black Diamond. I shoot 320 grain REAL conicals and they do real good. I also have had great luck with the T/C maxi ball in 370 grain I think they are. They shoot really good with 100 grains and would get excellent penetration. If your distance shooting was not to far away, I have also been shooting a 533 grain conical with 80 grains of Pyrodex RS. What a monster. But very accurate. I have shot them only out to 50 yards. I was going to try it further but was having so much fun shooting the big conicals, I shot them all off. These would penetrate anything, and the damage they would do inside should be tremendous, although the conicals I have recovered were not as expanded as I thought they would be.
Some of the hand cast bullets I am shooting are giving excellent groups, but they are not something I would elk hunt with. I tried the powerbelts, and they did not shoot well at all. I shot a 4" groups with them. With my scoped rifle I expect more then that from a projectile.
Have you people that own BD's noticed that the max powder charge range is about 120 grains? Not that I am all upset over that. I never intended shooting 150 grains of powder, but anything over 120 grains and they groups really open out. 100 grains seems to be the average powder charge for most projectiles. Have your rifles been different?
I was shooting at 200 yards a couple weeks ago just to see if I could. With the Shockwaves, I was holding a 6" group from the bull. This was off shooting sticks, so considering a elk hot zone is 8" I was told, this would have all been lethel shooting. I was real happy. It is the first time I ever tried to do it. I want to go on record, I would not shoot that far at an elk with this rifle. I am not sure of the energy at that range and I am not tracking anymore then I have to.