That is a wonderful rifle you have with a great family history. A former naval officer friend used to tell me what a sensation the .22 Hornet was when it came out in the 1930s, how flat it shot, and how it was instant death on varmint critters. It was the first of the high velocity .22 cartridges, of course, but pretty modest performance for today.

When I used to load cast bullets for the .22 Hornet, it was always using linotype for the alloy. It was a gas check design, and there was no leading at the approximately 2000 fps velocities. I'm sure you can find commercial gc linotype cast bullets to duplicate this performance.