I've been shooting my MiHec 359-125 HPs in front of 3.8gr on HP-38 at 1.085" OAL for a little bit now. The speed is averaging ~1040fps and I seem to be getting terrible leading in my pistols.
I'm casting 20:1 air-cooled which should be a BHN of 12. I've read tons of data of people pushing 20:1 up to 1500fps without leading, so I'm confused on what I'm doin' wrong. My smallest pistol slugged at .355, the largest at .359, and the carbine at .359. I'm sizing them down to .358 so in theory, they should be fine. I cast pure lead bullets for my air rifle so I prefer to make my own alloys over mixing with WW, since I buy pure lead anyways. Though I'm at a loss at why I'm leading so badly. The load is mid-range, the speed is not overly fast or slow, the BHN is on the softer side (but not overly so for the speed), and my boolits are reasonably sized for the barrels.
I'm thinkin' I'm going to try water quenching the next 300-400 boolits to increase the BHN slightly. From what I've read it should go to about 15 considering there's no antimony in a 20:1 alloy.
I know eventually playing with all the factors I'll figure out the cause and correct it, though I'll take suggestions. That being said at the moment I'm not looking to change to a WW alloy.
This is from my father's Kahr CW9 after about 300rds. (I know, terrible photo)