yes, it is easily done IF it is just lead and tin. But in all likelihood you probably have antimony in there too and that means you have 3 unknowns and only two independent equations. In other words, "What ClapperZapper said".
I calculate lead-tin ratios for casting all the time and have a spreadsheet set up for it to make it simpler, but it's only good on PB/SN alloys.
Care to share your spreadsheet, Brent? I am 99% confident the 1880s bullet is lead and tin only, and does not contain antimony or mercury. Thank you very much
