Bruce, here's a snippet from a post I copied off this forum. This alloy formula has worked out quite well for me, hope you can make use of the info.
copper alloy
Bullet Design: RCBS 30-180-SP (Late version, bore riding nose)
Actual weight lubed & checked: 190 grains
Cast of an alloy that is: (according to Badgeredd's alloy calculator)
92.35% Pure lead and other trace elements
3.73% Tin
3.5% Antimony
.22% Copper
.20% Arsenic
The easy way to mix this alloy is to follow this simple recipe of 8 lbs. Clip On Wheel Weights, 1.5 lbs. of Pure Lead, and .375 lbs. of Rotometals Grade 11 Babbit for a 10 pound pot. Double the amounts for a 20 pound pot and quadruple the amounts for a 40 pound pot, etc. Here's a hint, don't assume that your soft range scrap is in fact pure lead that's ok to use in this mix, it probably isn't. Use what this recipe calls for, don't deviate. There are enough variables to deal with in Clip On Wheel Weight alloy as it is. No need to have the other components skewed.
Bullets were water dropped from the mold into a five gallon water bucket. They were allowed to stabilize for two weeks, BHN was 28, sized/checked to .310" diameter and lubed with MML + 5% Soap. My mold casts a bullet nose that is .302" diameter using the above alloy from my mold.
The load itself is as follows: (loaded and shot as projected in Quickload)
46 grains of IMR-3031
CCI #200 Large Rifle Primer
54,000 psi / 100% powder burn / muzzle pressure = 7,849 psi
5 shot average over the chronograph is 2,510 fps