Also I was wondering if someone would know the best way to mix the plumbers lead of 8 BHN to achieve a BHN of around 15 or so for the higher velocity on the .357? I was going to stay with this caliber until I can get better with the casting technique, because I am seeing the difference in the bullet weights with the casting and I need to work on getting them a lot more consistent, if anyone has some ideas they will be welcomed
Alloy effects Bullet weight. A lot of other factors. Check for square nice bases first, round edge ones are light pours and can cause other accuracy issues besides. Chunk those, or put them aside for close up plinking fodder where accuracy does not count.
A lot of times I find myself weighing the bullets into + or -.3 lots. Then save the 2 closest to the expected weight groups. The rest go back into another melt.
Trust me for hotter .357 loads, go for 12 first, and a good fit. Rather then 15 BHN.
Still use the softer stuff for your light loads. 8bhn is great for light loads.
15 can cause leading, flame cutting etc., in your .357
12 BHN is just where lack of arbitration starts to be a factor. Not getting good expansion, to get a good seal, This is needed if your sizing is not just so to match the gun. 12 is still way more forgiving concerning fit then 15bhn (lyman#2).
12 likes the hotter top of the spectrum loads for .357, but will bite you in the butt in what we call the "mouse fart" loads.
How do you get 12? Easy way... check a wheel weight bullet un quenched if it reads 11 or12 use that. If it needs adjusted then.... Straight from Roto Metals Web sight......
Basic Rules for Hardening Lead-
(go by weight, not volume)
For every 1% additional tin, Brinell hardness increases 0.3.
(you can use pewter, tin pellets; or you can use 50-50 solder x 2.2 for tin)
For every 1% additional antimony, Brinell hardness increases 0.9.
For a simple equation,
Brinell = 8.60 (Antimonial Lead) + ( 0.29 * Tin ) + ( 0.92 * Antimony )