There is an online pdf for the complete Lyman Manual #4. Staring on page 43 there is a multi page scientific article how the molecules interact for alloy hardening & softening

Rockwell Testers use a Ball penetrator for Brinell Hardness. Also a Rotatable 
weight system for the Brinell load. In the Rockwell Scale when you get material 
below 28-30 Rockwell it becomes unreliable. In Brinell if you have it setup right the indicator face has a Brinell scale so you can read it directly. Now the SAECO hardness instructions indicate you can recreate Alloy by meeting certain hardness and thus create the same as pure lead Tin alloys. WRONG!
Alloy is alloy, Lead, Tin means  LEAD/TIN only. The one constant that is lost is Chemistry. For many years I have been told by Men who would say "Antimony and Black Powder don't MIX" I was at that time using Linotype 
as a Base for making my Alloy's up and checking hardness by squashing a bullet of Known alloy and my fresh Alloy against each other both from the same mold, when they squashed flat they were the same. NOT SO. The Alloy would on occasion throw a flier that I called good. Finally the Black Powder and Antimony struck a Bell. Sold off all my made up Alloy and went to Pure Lead, Pure Tin and the Fliers LESSEND, my score went up. Now wrote the occasional fliers off to ME! My son is a Material Science Professor at UVA in 
Virginia. We have had this conversations more than a few times and he has made me aware of some of the flaw's available with mixing Alloy's with more than two materials. Once you start that you lose all real control of what you produce. He gave me some advise on the Benefits ? or Flaws of dropping bullets into a Bucket of Water. Will elaborate on that if it would be of interest.
But this conversation started as a Hardness figure. So we can talk about the water quench at another time. FITZ. OLD TUCK

John I do agree with you. But the issue of very exact materials can only be determined by a shooter using superb Bench shooting and or Machine rest 
techniques.
As you know my interest has always and still is Offhand shooting. I do no bench shooting of any serious level. So all my evaluation of a load or rifle is done offhand. Now to be completely honest, you cannot get absolutely clear
results offhand in one test firing. Some day's you will do well and some day's poorly. BUT, if I go to the Range 3 or 4 weeks in a row and shoot good targets then I can be sure of a couple of things. A) I have a good Load,
B) The Rifle is a Shooter, C) It is Zeroed. You just cannot be lucky over 3 or 4
weeks. When I get one of my "Hale Mary shots" where it settles in and settles down and when it goes off and I am surprised and my follow though is good and the bullet hole shows up right where I saw the Cross Hairs when it went off. Then I am good with the world and I know I have going combination. Now again being Honest those day's are fewer now, I am older now and nowhere as strong as I once was. So I have fewer of those shots. HA! But I do have a significant Herd of rifles and documentation of what they are capable of. That's My Story and I am sticking to it. Regards, FITZ.OLD TUCK