Understanding how alloy work.

[Casull]

Can anyone help me understand what i might be doing wrong with my alloy if im doing anything wrong at all? My mix contains
Tin 7.37%
Antimony 5.88%
Arsenic .27%
Lead 86.5%
The bumpo calculator says that should yield a BHN of 16. I cast this mix into ingots for now and 21 hrs after im getting a BHN of 12. Is this normal for a 21 hr old cast should i give it a week then re test the ingot. The reason this is a concern is because they will be for 454 casull rounds. They will eventually be a perfect fit and gas checked. Im just trying to understand how to get a solid bullet before heat treating. People seem to be able to get bhn 12 using crap then heat treating up to 25. I cant seem to pass 12 bhn no mater what i use.

 

[troy fairweather]

Do you water quench them?

 

[reddog81]

21 hours isn’t very long at all. Wait a week or 2.

How are you measuring the BHN? What do you mean by heat treatment? Any heat treatment will typically lower BHN unless your water dropping afterwards.


Why so much tin? That a very expensive way to make the bullets marginally harder.

 

[kcofohio]

I'm new to casting, I mean really new.
But from what I have read, I am curious. How are you mixing the antimony into your lead? And do you add tin at the same time?

http://www.lasc.us/Fryxell_Book_Chapter_3_alloySelectionMetallurgy.htm

 

[jmorris]

The numbers I cast to are weight. I have one mold I use as my standard, with different alloys I can get it to drop from 240 grains (pure lead) to 210 grains (silver solder). I mix my alloy until it drops as close to 230 as I want for the job. Pure lead will make the mix heavier, lynotype makes it lighter.

That said, I coat most all of my bullets these days and that may even be a waste of time but it’s still a habit.

 

[tightgroup tiger]

Why so much tin?

I'd like to know why so much Arsenic? Why any at all? There should be no Arsenic in bullet alloy unless your trying to make frangible lead bullets in which you'll die of Arsenic poisoning before you get there. Arsenic makes a lead alloy brittle but makes it strong to handle heavy weight.

I expect this mix of yours is seperating and your left with lead and a little tin. Antimony in lead has to be cast at a higher temp or the Antimony separates out. The rest is going out with your dross and the Arsenic is evaporating.

I hope your using it out doors and your staying up wind of it.

Where are you getting this alloy of yours and how do you know what's in it?