Lead-tin age hardens????

[Jack Stanley]

The other day I drained the pot to change alloys with the intent to make up a soft lead-tin mix for hollow points for the .38 special . Had twenty pounds or so of pure lead in the pot , cast a few slugs to test on the LBT tester . The slugs didn't even register .... it seems to me pure lead should be about five BHN . So I started adding tin .

It took over a pound of 50-50 solder to make the test slugs register a six on the scale . At a guess I'd say I put about 1.6 pounds of solder into the alloy and it just seems it should have registered a bit more . The really odd part is this , I measured a couple slugs this morning and they were in the eight BHN area .

Perhaps the tester is off to begin with , that I can understand . I was with the understanding that lead tin alloys did not age harden . Can someone who has worked with this softer stuff enlighten me . My normal route is use soft scrap alloy and harden with linotype so I am on a new learning curve I guess .

Thanks , Jack

[williamwaco]

Tin adds very little to the hardness. Antimony is used to make it harder. To harden up pure lead you need to add some wheel weights or some type metal with a high antimony content.

Rotometals http://www.rotometals.com/Bullet-Casting-Alloys-s/5.htm Sells very hard alloys for the purpose of hardening up or adjusting alloy content.

[R.M.]

LBT testers don't read accurately at pure levels. One of their weak points. It sounds like you added way too much tin.

[cbrick]

LBT testers don't read accurately at pure levels. One of their weak points. It sounds like you added way too much tin.

Really? Mine sure seems to, it says right at 5 with straight Pb.

Jack, no way to know how much tin you added other than possibly 1.6 pounds. Did you add it to a 5 pound pot? A 10 pound pot? A 20 pounder? Are you using the Magma 40 or 90 pound pot? See what I mean?

Enough tin can get you to 8 BHN and it may take a day to get there but I would be very surprised if they get any harder, depends on how much tin, how much lead. So yes, tin does harden lead but minimally unless you go nuts with it. Without looking up the exact numbers (from memory) the hardest tin can make lead is something like 15 BHN at something like 65% tin (solder). Very expensive, very lite weight bullets.

Rick

[Jack Stanley]

Thanks R.M. Perhaps I should take about five pounds out of the pot and then add five more of pure . All I'm really trying to do is get an alloy that will cast in a 358439 real well and expand good at 850 to 900 feet per second or so .

Going this route is just a little different for me than adding antimony to scrap to make hard alloy . Like I say , still learning about soft lead alloys .

Jack

[R.M.]

cbrick, I'd have to dig up the instructions that Veral sent with the tester, but I'm sure I read that he didn't recommend it for testing pure. http://lbtmoulds.com/hardtester.shtml
When I try it out on pure, the needle barely registers.

[cbrick]

The closest to pure I have right now is stick-on WW which mormally says 6 BHN. I'll try some of that again and see if it still does.

Rick

[Whiterabbit]

Jack, I was reading I think castpics or lasc (is that it?) the other day on alloys, and I believe I read that lead-tin age softens, not hardens. Where lead-Antimony is what age hardens.

No empirical data yet. You'd have to go wheel-weight-less with your lead and go for straight pure-lead/solder to test that, methinks. To make sure you had no antimony in there.

[geargnasher]

Whiterabbit has it right: Lead/tin binaries are at their hardest as soon as they're cast and cooled. They soften to their final hardness in a short time. I've tested foundry 16:1 at just shy of 11 bhn with a Lee tester three days after casting, which confirms what Elmer Keith said a lifetime ago.

Gear

[Jack Stanley]

I'm certain there was no antimony was in the mix . I tested slugs yesterday and today and both readings came in at just under eight on the LBT scale so I'm gonna call it about forty to one . I understand that using lots of tin in the alloy could cause it to age soften here's a question for those that know . At what mixture will tin/lead alloys remain the same over time ??

In the 358439 I'm casting it in and loading in .38 special cases with 5.5 of Unique I can only hope it will ruin the day of any woodchucks and other small critters trying to infiltrate the perimeter .

Jack

[cbrick]

Yes Whiterabbit is correct but, that's Pb/Sb/Sn alloys and they age soften very slowly. I tested HT Pb/Sb/Sn bullets at 30 BHN, stored away for 10 years they were 26 BHN. It is also correct that the higher the percentage of Sn in a Pb/Sb/Sn alloy the faster age softening will occur but again, slowly. It doesn't mean that you need to shoot them by the end of the week. That is how I have it on the lasc site.

I don't know if I have ever tested a PB/Sn alloy the day of casting and then the next day but by the next day they should be stable for the foreseeable future.

Gear is also correct, Elmer gave birth to the 44 Mag with 11-12 BHN Pb/Sn alloy with PB bullets and Elmer was a happy man.

Jack's 8 BHN 38 Special bullets should work very, very well making Jack a happy man.

Rick

[runfiverun]

30-1 or even especially 40-1 should mush right up at 800fps with no problems.
40-1 was used by winchester and remington for a long time in their 45 colt loads and others like the 44-40 and most likely the 38 special round nose loads from earlier times.
elmers 16-1 come straight from trying his hotter loads with some of those factory boolits [at least the alloy] and wanting a better way.
he also used 20-1 for many of his loads.

[ripshod]

My LBT tester reads like yours does.Pure lead reads between 3 and 4.I made some 20 to 1 alloy and it read 9 if I recall properly.I think my tester is about 18 years old.ripshod