Has anyone heard of this or know anything about it?
Years ago, my shooting buddy (RIP) would cast his .357 boolets with a Zinc washer as a gas check. I think he had a special mould for this. He said Zinc is a natural lubricant for steel. If I remember correctly, the zinc washer was in location where the lube groove would be because he did not lube these boolets. We shot thousands of these from various pistols at or near jacketed bullet magnum velocities.
Mark