Why Does Lyman #2 have 5% Tin?

[Jeff82]

I'm planning my next batch of alloy, and am wondering why Lyman #2 has such a high tin percentage. My references say 5%. My understanding is that beyond about 2%, there is really no advantage to adding more tin. Am I missing something?

[9.3X62AL]

Only recently have I started casting with Lyman #2 alloy, and my initial impression is that fill-out in Loverin-type designs with multiple small drive bands is easier to achieve than with my usual 92/6/2 alloy. Both alloys have an almost identical Brinnell Hardness rating, 14-15.

My recollection--and I can't recall its source--is that as a general rule you gain nothing by adding more tin than antimony to a tri-metal alloy in terms of hardness. Given the high cost of tin these days, I'm prone to believe that #2 alloy comes from a time when casting metals were far less expensive than present days.

[lwknight]

The 2% tin theory is to save tin because it is expensive. Very little tin is actually needed to help casting.

The 5% tin aka #2 uses tin for more hardness and toughness not for castability. ( is that a word? )

Then comes hardball or 2-6-92 where antimony is used in place of tin to get about the same hardness. Reasoning is that at the time , antimony was really cheap.

So there are great advantages to higher tin content when you need it. Lets face it, most casters are really cheap skates at heart and hate to spend their money. Once we learned that all that much tin was not required for most applications we shared the info.

[lwknight]

and I can't recall its source--is that as a general rule you gain nothing by adding more tin than antimony to a tri-metal alloy in terms of hardness.

Although you gain far more by adding more antimony than tin , this does not mean that if you need a high tin alloy that some accidental antimony in the mix will not work out. When you want more ductility you simply overwhelm the antimony with tin and pretend that it is not there.

lwknights' tin antimony rule is no more than 3 antimonys to 1 tin. Tin makes antimony behave in the alloy.

[GRid.1569]

castability. ( is that a word? )


It is if everybody knows it's meaning.... :smile:

[sqlbullet]

The extra tin adds a bunch of malleability. This is useful in terminal ballistics.

For punching paper it is not needed.

[Defcon-One]

I am a fan of Lyman #2 alloy. I am a bit cheap, like we all are, and can't see sending a bunch of Tin down range for handgun loads, plinking, etc. However, for shooting rifles with cast, gas checked bullets at higher velocities and longer ranges, I use Lyman #2 Alloy almost exclusively. I have used Linotype as well, but find it too hard and too hard to find to waste it on something that can be accomplished just as well with Lyman #2.

The Tin is for toughness and castabilty, no question both!

The Antimony is for hardeness!

The Lead has a high mass to volume ratio, flows well in solid form and is relatively inexpensive!

Put all of them together at 5% Sn, 5% Sb, 90% Pb and you have what I consider a Wonder Alloy!

And this is why they are matched 5% Tin to 5% Antimony:
Tin makes antimony behave in the alloy.

[popper]

I used #2, then 50/50 Pb/#2, now just get high Sb/Pb(rotometal). So far cast-ability is fine for 40, 30-30, 308. I do add As or S to solve the Sb problem. For 40, I cut with 50% Pb. Just enough Sb so I don't have the case resizing the CB when loaded.

[geargnasher]

Why? Several reasons. First, tin and antimony in a lead solution form an intermetallic bond wtih each other, creating what is in effect another elemenent within the mix, called Sb/Sn. This is called an "intermetallic bond". Sb/Sn is both more tough and more malleable than either Sb or Sn alone, and imparts some good characteristics to the alloy when casting and when being fired, as well as when being used for hunting.

Sb and Sn combine in approximately equal parts in solution, so any ternary lead alloy containing Sb and Sn in equal proportion will behave as a binary lead/(Sb/Sn) alloy.

All ternary Pb/Sb/Sn alloys contain Sb/Sn in the proportions that will combine. For example, 92/6/2 alloy is really 92Pb, 4Sb/Sn, and 4Sb, with no "free" tin. Overtinned alloys do have free tin, due to it's melt point and the order in which the elements freeze tin will be the last to freeze and gets pushed out of "solution", forming tin "nodules" which are not conducive to a lead-free bore. Not enough tin and too much antimony often results in "Antimony wash" in the bore, which is a haze of hard antimony "dust" that shears off of thd surface of the boolit and iron onto the bore. Most of the time antimony haze isn't an issue as long is it isn't so severe that it accumulates, but a pinch of tin easily takes care of the issue.

Lyman #2 with 5% each of Sb and Sn has one more neat quality: It's a pseudo-binary eutectic, meaning it has no mush phase between solid and liquid, so it behaves like pure water freezing or melting.

Gear

[popper]

Minor detail, Sb/Sn will combine and de-combine over weeks till it stabilizes, at room temp. Ratios are also a function of cooling rate.

[Idaho Sharpshooter]

Quick Answer: tin used to be cheap, and readily available pure or in alloy. Lino was usually the only way to get antimony in an alloy. Back in the early seventies it was common to mix
Lino/WW/lLead in a 2/5/5 alloy in everything except shotgun slugs/buckshot.
It shot well in old Lyman 311284 and 311332 in 30 caliber rifles.

Life was much simpler back then...

Rich
Sua Sponte

[NYBushBro]

A hundred years ago (or perhaps less), RIFLE alloy was considered 10:1 Lead:Tin (Pb:Sn)... it is my guess that LYMAN found a cheaper way to produce a 10:1 alloy that had a bit more hardness to it (antimony has probably ALWAYS been cheaper than Tin, even way back then.)
NOTE: if you doubt this, look up at CASTPICS website under 'historic mold catalogs' the RECOMMENDED alloy for the Modern-Bond molds (inter-war mold company).

Besides, the newspaper trade was a bit more bustling back then (pre-TV and internet) so there was a steady source of 'scrap' metal... which might also be why wheel-balancing weights have been made of diluted linotype for the past 50 years.

I would actually like to try some 10:1 mix, JUST to see how it expands.

[lwknight]

I would actually like to try some 10:1 mix, JUST to see how it expands.
My guess: It will be way too hard for handguns.
Then again I never tried it.

[Idaho Sharpshooter]

Elmer Keith, one visit to his place in Salmon about 1978; he used 16:1. He was casting (surprise!) boolits for 44 Magnum. He said that was about all he ever used, the pistols did not lead beyond a single patch w/Hoppes #9, and it gave a great balance of penetration and expansion.

Actually, he was supervising his runner Ralph Graham who was doing the actual casting. My function was keeping ice cubes coming from the house, and taking notes of the actual alloy of Coke and Chevas. Yes, he mixed, even in mixed company.

Rich
Sua Sponte