To answer several questions...
I was shooting a 0.490" ball with 0.015" Ox Yoke patch lubed with mink oil tallow from Track of the Wolf. This was pushed by 90 grains of Swiss 3F powder. This chronographs at 2000 fps MV. The ball was cast from wheel weight lead. The severe flattening of pure lead balls made me question their suitability for elk, where penetration of 30" or more might be required. That led me to the "Cast Boolits" forum and ultimately to wheel weight lead.
A fellow who founded Cast Performance Bullet Company put me on to using WW lead. He told me, "If you read the writings of Southerland, Forsyth, Clifton, Cody, and Ashley you'll see ALL of them recommended hardening the balls." He also told me, "I once shot 4 balls into 1 1/4" at 100 yards with a 54 cal FLINTLOCK over a rest, and I did it with WW balls."
As for accuracy of wheel weight lead balls, see the 50 yard target below. I fired 10 shots of my hunting loads, though only 9 are clearly distinguishable.
The bull had been coming towards me at a slight angle. I shot him in the chest just to the right of his right front leg. The ball passed diagonally through the chest cavity, taking out both lungs, and stopped just under the skin on the far side. The ball had broken into two pieces, which I found side-by-side. Deformation of the two pieces indicates the ball hit something hard that caused it to shear into two pieces. Most likely this was the far side rib. If the ball had broken on hitting the front rib, the two pieces would have diverged as they passed through the chest cavity.
When I shot him, he staggered then turned and stumbled away on three legs. He dropped after 40 yards.
I built the rifle. It has a .50 caliber 38" Getz swamped barrel, Davis double set triggers and a large Siler lock. I had the muzzle coned to ease loading. Metal engraving was done by Greg Dixon of Dixon's Muzzleloading Shop in Kempton, PA.