The curiocity never ends

[Kurt]

John I have no idea what that alloy was. It was indoor range scrap that I have a bucket full of I use for hand gun alloy. My main interest with these couple loads with the 121 was to see if the .45-70 round would survive gas cuts shot with the .45-90 with the five degree chamber end.
Your 97-1.5-1.5 is the Lyman #1 alloy that is not much mentioned anymore. Harry Pope used to use it a lot and you can find it in the Ideal cast bullet manuals. If you have a lead tester I think you will find it closer to 1/25. It's that small amount of 1.5 % of antimony that will hold the nose so well.