What range of BHN should I try to achieve for my .45-70 cast bullits?

There are three different "classes" of rifles that shoot the old cartridge, and they differ because of strength. Depending on which one you own, you can go anywhere from as soft as 30:1 lead/tin ratio to pure linotype. It all hinges on expected projectile velocity...

Oh yeah, I forgot that part. It is an 1884 trapdoor with a new green mountain barrel screwed on it. I will be shooting stricktly BP in the cartridges. At the moment I have a lee 500 gr mold. The mold might be 525 I don't remember so I will wiegh the finnished product before I load them. From what I'm reading I should expect 1100 to 1400 fps from them but I can't swear to it because of memeory problems. I made my own lube from 50% soy wax, 40% crisco and 10% canola oil. Pan lubing is the plan.

Otto
anywhere from 8 to 12 BHN should do it.

you can get there with 30 to 1 tin lead on the low side

20 to 1 on the high side

or wheel weight metal.

Check out the LA cast bullet web site or Cast Boolits


the tin lead alloys cast easier than wheel weight alloy

I think wheel weights are going to be too hard. It will take a lot of lead and a lot of tin, but somewhere in the 1:20 or 1:25 would be my recommendation. I used 1:20 in my #3 Rolling Block, and it worked quite well with 65 grains of black...

Experience has shown that BHn X 1442 (courtesy of Ed Harris at the NRA)is the minimum yield strength to shoot for. 14,442 PSI is a bit past the original BP loads, IIRC.

Rich

SR, thanks for the websites.

Forget the wheel weights for this application. Work with the 20:1 and/or 30:1 lead/tin suggestions. Your rifle may show a preference for one over the other. You want soft...in a BP cartridge, "bumping the base" is a good thing. Too hard, and it won't happen in a relaible, uniform manner.