Many find 20-1 alloy a good one. However, the arsenal did a considerable amount of testing of alloy composition among a lot of other things back in the 1880s before adopting the 500 gr bullet. They found an alloy of 16-1 was better. I tested both the 20-1 alloy and the 16-1 alloy some years back at 600 yards and found the 16-1 alloy was, indeed, the more accurate with full service level loads of 70 gr with the 500 gr bullet running 1250 fps +/-.