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View Full Version : Alloy hardness changing over time.



Martini Sportco
03-21-2020, 08:41 PM
Hey all,
What is the general consensus on cast bullets getting harder or softer over a period of time.
I usually knock out about 100 bullets at a time per mold, cast from ingots that I have made previosly. Those ingots are made up of Lead / Tin which I test with a Lee hardness tester and could be 6 months old. Every once in a while I notice the bullets seem to be harder, ( I breach seat with a hand push seater) and when I re test them, they are actually harder. Not much, (30:1 goes to 25:1) but enough to make the seating difficult even with Tapered and Base band designs. Why is it so. When I test the ingots during manufacture, obviously the alloy is new and still warm, does it change over the next 24 hrs, 48 hrs, 2 weeks ??.
I buy used Plumbers flashing and lead pipe from the Recyclers which tests very very close to pure, as far as the Lee Tester is concerned.
I buy old Pewter mugs etc for my tin. Do either of these ingrediants have the ability to change over time ? If they do, then I should have had this problem every time I've cast, for 20 years, because I have never bought new pure lead or tin. I don't use Range lead, linotype or wheel wieghts. I don't use a themometer. Any thoughts ??

John Wayne
03-21-2020, 09:30 PM
Yes sir, it will all harden over time. I've never been very scientific about it but I'm sure someone else will chime in with more detail. Cast a lot more than you need and water quench will harden some too.

Dusty Bannister
03-21-2020, 09:53 PM
Pure lead and tin will not age harden over time. The antimony in the lead plumbing pipe and fittings does slowly age harden and may expand a bit as it ages. Refer to the LASC site to become better informed on how the metals behave.

Dieselhorses
03-22-2020, 01:07 AM
I was testing the hardness of ingots (CWW) before I melted in Lee pot. Found out quick that casting new bullets basically started the hardening process over again. My ingots run usually 12 bhn a few weeks after pouring then 6 months + reach 17 bhn . I powder coat everything so I just watch not to get anything too hard. Like Dusty said, refer to LASC website for accurate info (I find myself going back there from time to time!)

unclemikeinct
03-22-2020, 01:48 AM
Your Pewter mugs are the source of the Antimony in your alloy. That stuff will harden lead . Check the blend tables. uncle mike