I have a 3-screw Ruger Blackhawk 357 from the 1970's. Shoots great but has had a leading issue in the forcing cone and first part of the barrel. I had the cylinders all reamed out to 0.3575". The bullets are a commercial hard cast 358 SWC PB at about 19 BHN, not sure of the lube. They are all 0.358" and I have a bunch of them. At 950 fps with 4.5 gr Unique it leads. I increased to more of a 357 velocity of 1,100 fps with 5.8 grains of Unique, it still leads. My calculations said the faster load is 27,000 psi. Dividing this PSI by 1920 says 14 BHN is what I should use and dividing this PSI by 1,422 says that 19 BHN should work but is as hard as you really should go. My question is should I keep pushing the velocity up hoping to get the bullets to bump up more? Alliant data says I can go to 6.8 grains of Unique for 1,250 fps and 33,600 psi. I have never slugged the barrel, and I do not know what the forcing cone angle is.
Happy Thanksgiving to all!