I need some help hardening lead with copper sulfate. I've read the sticky, searched a bunch of posts but still having trouble. The alloy I have used for years is 2.5 Sb, 2.5 Sn. Very similar to WW + tin, tests to 12 BHN. Age hardens to 13-14 BHN. It has worked fine for years but I recently started casting HP. The feed ramp on my semis is deforming the nose, affecting accuracy. I think the copper hardening would be the perfect solution.
I tried Popper's copper sulfate method. Heated the lead to 750+, layer on the copper sulfate, cook the moisture out, break up the crust, stir back into the melt, flux is into the melt, stir some more..... Resulting ingots test at 10 BHN. I let is age a couple of days and no change. I repeated the procedure and dumped the dross from the first try on top. Added some more copper sulfate and result is still 10 BHN.
Anyone have any ideas?