Author Topic: Bismuth in Alloy  (Read 765 times)

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Offline BABore

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Bismuth in Alloy
« on: September 17, 2007, 03:13:13 AM »
Veral,

Could you please explain to me, the effect of small additions of Bismuth to a lead alloy. I've heard it works similar to antimony in its hardening ability upon quenching. How is the brittleness factor.

I typically cast my bullets from 50/50 WW-Pb. It will drop AC'd bullets at 9-10 Bhn and achieve 18-22 Bhn either WD'd or OHT'd. Full hardness is usually achieved within 10 days. Hardness after quenching is usually 12-13 Bhn. I like to shoot a few, with the same load, at various stages of hardness to get a feel for what the most accurate alloy hardness will be.

Part of my pure (soft) lead ingot bucket was from some range scrap I had gotten for free. Indoor range, lots of 22 LR bullets used for competition, high end foreign ammo. I wasn't aware that they use bismuth in some 22 ammo.

Anyway, I found a load for one of my lever gun's that seemed to prefer an alloy hardness of 16-18 Bhn. I let my 40 lb 50/50 pot run down about a third of the way, then topped it up with my soft lead, shooting for a 35/65 WW-Pb alloy. From past experience I knew this should WD at the appropriate hardness. I tested a couple bullets right away and found them to already be at 20 Bhn. After a week they were at 28 Bhn. Oops! A friend told me I had probably inadvertially added some bismuth to get that hardness, that quick. As I only have about a half of a bucket left of this bismuth alloy, I'm going to hardness test the ingots to see if I can sort them out.

If this is truly bismuth doing the extra, and fast hardening effort, what's the downside if any. I've also heard that bismuth will retard any after cast diameter growth. The opposite of antimony

Offline Veral

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Re: Bismuth in Alloy
« Reply #1 on: September 17, 2007, 05:59:02 PM »
  Your information is quite informative, because I had no idea that bismuth was ever used in lead alloys, nor can I help you on amounts to use or what it will do with hardness.

  Please keep us informed, and I suggest that you contact Bill Furguson                      bulletman1@cox.net                    He's proabably as good a lead metalurgist as there is in the country, and a good source of various lead alloys as well.
Veral Smith deceased 1/19/25