If you know your lead supply, it is not really needed IMO. Pure lead will normally scratch very easy. The more alloy in the lead, the harder it gets and more resistant to a sharp object like a nail. I've casted for years and never used a lead tester. Another way to test the cast bullet is weight. Lead projectiles will weigh more then ones cast from a mix. For instance my Lee mold that is supposed to produce a 405 grain bullet throws a 423 out of pure lead most the time. When I asked LEE about this they told me it was the difference in the lead purity. Yet, when I cast a roundball and they are supposed to be 177 grain, they normally come out 175-182 in weight. This is just casting differences. If you cast them with wheel weights they come out much lighters. I can't remember the differences anymore. Or the Brinnell Hardness Numbers of the different mix but casting is a lot of fun, and there is a lot to learn about it. I am still learning all the time.