It's hard to find laboratory data on bullet strength and all too often casters rely on rules of thumb that are not good rules (I'm talking about you, 1422X forumula ! ).
What little data exists is usually for solders because apparently solder companies care about strength enough to actually test it. Here is some data found at this link:
And here is more solder data, if you don't mind converting the metric units to psi.
Let's take 10:1 alloy, with a tensile strength of 4400 psi and a BHN of 11.5. Linotype is about twice as hard so it's reasonable to assume that linotype would also be twice as strong -- 8800 psi. Heat treated wheelweight would be 3 times as hard so it's reasonable to assume that it would be 3 times as strong -- 13,200 psi. That's just a quick and dirty way to look at it, but it's a reasonable ballpark estimate. Lead is not made out of steel, folks.