YOU can do a couple of things to get more penetration on Bear:
1. Use lead balls cast from alloy lead- that is, lead that contains tin and antimony. This makes the lead harder, and it keeps its shape and penetrates further, to reach vita organs, even after hitting bones.
2. Use a larger caliber rifle-- .58, .62 etc. to get a larger ball that weights more and penetrates further.
3. Where its legal, use two PRBs in that .50 caliber heavy barrel rifle in front of one powder charge. Out to 50 yards, which is a long shot at most bears, the two balls strike very close together, and both penetrate well. Recoil is increased, of course, but hitting a black bear with two such balls from one shot fired is a lot of energy transmitted to the bear's organs, and two holes create more blood loss at the same time, along with greater shock to the nervous system.
Its believed that this is what the Mountain men, and the earlier, "longhunters" did when they confronted a bear, instead of a deer. The gun was carried with whatever PRB load the hunter felt he needed to kill a deer, so that on seeing a bear, all he had to do was seat another PRB down on top of the first.
None of us were there, and I have only pieced this together from some biographies and histories of the period where old men were interviewed about how they did things. I Have tried this load- ONCE-- in my gun, and was surprised at how close the balls strike on target. I was using 75 grains of FFg powder in the gun.