For testing there was a member of another site that worked with an xray tester at his job. He would test samples for 1 lb of lead per sample, this was before covid. He has put a pause on it for the last year.
The spreadsheet calculator mentioned above has this statement in the note section. Estimated hardness calculated by Rotometals formula: Brinell = 8.60 + ( 0.29 * %Tin ) + ( 0.92 * %Antimony )
No way will I use tin at 10%, too expensive. I seldom get over 1.5% tin, a couple of the most experienced casters on another site I frequent run mostly below 1%. We're using just enough tin to help fill out the mold, letting the antimony do the hardening. Again, my fastest rifle loads are 308 at up to 2500 and I stay below 3% antimony on those. Much above 5% gets brittle and I hunt with these loads so I don't want brittle.
