I tend to differ on that. I observed first hand over two days two kills on mature mulie does. One with a GPR, RB, 80 gr 2f goex, 180 yards through the lungs ball uner the skin on the far side. Deer walked about 50 feet.
The other a TC Hawken, 54 cal, RB, 80 gr 2f goex, at 30 yards, IDENTICAL hit. Ball under the skin on the offside. Deer walked about 25 feet.
I'm not an advocate of the mysterious magical killing power of the RB. Just reporting what i saw with my own eyes.
I've built four of the 54 GPR kits and they were all serious patch cutters. It's the way those barrels left the factory. I was at the time into firelapping of modern guns and so applied it to the GPRs and they were all cured.
You accomplished the same thing with hand lapping which is probably the simpler way of getting there.