And yet another source, from Wilhelm Hofman's book "Lead and Lead Alloys." Unfortunately my notes lack the page number.
To convert the ultimate tensile strength (U.T.S) in kg/mm2 to PSI, multiply by 1422.
5 BHN ---> 2.5 kg/mm2 = 3600 psi
10 BHN ---> 3.8 kg/mm2 = 5404 psi
15 BHN --->5.9 kg/mm2 = 8390 psi
Note that the chart shows that BHN and Ultimate Tensile Strength with the units "kg/mm2." It's true that they have the same units, and some folks seem to jump to the conclusion "if they have the same units, they must be the same thing !" Sorry but it's more complicated than that. Tensile strength, yield strength, shear strength, compressive strength, and hardness all have the same units of force over area, yet they mean different things.
Another question that comes up is "well that's just the TENSILE strength? What about COMPRESSIVE strength?"
The answer is that it depends. If the material is brittle, like concrete, or like monotype, then the tensile strength will be less than the compressive strength.
But if the material is ductile, as most bullet alloys are, then it's safe to assume that the compressive strength is the same, or at least about the same, as the tensile strength. Ditto most ductile steels.
It's always better to measure the strength of a material rather than making assumptions and relying on rules of thumb, but in real life engineers make assumptions and rely on rules of thumb all the time. One of those rules of thumb is that you can usually predict the strength of a ductile metal based on its hardness, to the tune of 500 x BHN = the approximate strength in PSI.