A method suggested by the NRA years ago was to sandwich a ball bearing between an ingot of pure lead and an ingot of unknown lead, and then squash the sandwich in a vise. The BHN would then be 5 BHN * (D_pure / D_sample)^2.
But that only works on ingots. How would you use it to measure bullets?
This is what I came up with.
I use a 45 caliber cylindrical slug for BHN and density measurements. In any event, 45 is a popular caliber so many casters will have a mold for a flat nose 45.
I cut a piece of 1/2" pex pipe that was slightly shorter than 2 cylinders and the 10mm ball. The pex serves to hold the cylinder sandwich together during the test. Put the sandwich in a vise and squash them.
That was easy!
However, the pure lead slug obturated so much that it was stuck inside the pex.
To get it out, I ended up slitting the pex with a utility knife. That's OK, the slitted pex still will serve to hold the cylinder sandwich.
Results, as measured with a USB microscope:
D_pure = 0.299"
D_lino = 0.1535"
5 BHN * (D_pure / D_lino)^2 = 19.2 BHN
That compares to 21.7 BHN for the 10mm / 150 kg test. At least it's in the ballpark.
I'll run this system through its paces with other alloys and we'll see if it continues to give ballpark accuracy.
-- cheap, cheap, cheap !
-- if it indeed gives reliable ballpark accuracy, that's more than you can say about some hardness testers.