BRAIN MALFUNCTION
Should have said 60 tin, 40 lead. This, or better 63% tin 37% lead, is the lowest melting point solder available. This makes life a touch easier when casting the nosecap.
Original half-stock rifle nosecaps were of some alloy containing lead. That is why they have a somewhat dark color.
Antique pewter contained lead, which gave it the same color when aged. It also poisoned those who liked to eat tomatoes from a pewter dish. So, modern "Britannia Metal" is an alloy of tin, copper and antimony, with no nasty lead in it. Makes a nice shiny nose-cap but that will look modern, not like the rifles Mr Leman made.
Please do no use aluminum.