You do need to know what your alloy is. Pure lead will be too soft and will lead something terrible. A hardness tester will get you there, but there is another option. Many pawn shops now have XRF machines that they use to verify jewelry with. They can use it to determine the alloy in your lead and there are charts that will give you the hardness based on the alloy. If you are friendly with one, they will likely test a sample for you and tell you what you got.

You can add tin and antimony to get the right mix. Tin can be had from radiator solder, something like 50/50 is 50% tin and 50% lead, adding to the mix can get you where you need to be. You can also order the metals online, seems like rotometals is one dealer.

Rosewood