Alloy composition

Kevin Stenberg

Well-Known Member
I always read that tin should be less than antimony. But i have never read why. Could someone tell why the tin quantity should be less than the antimony quantity?
 

Cherokee

Medina, Ohio
I always understood it was because higher tin would tend to stick or act like solder in a 3-metal mix - from my dim memory, maybe, sorta.
 

Pistolero

Well-Known Member
I think the main reason for our purposes is that tin is expensive and beyond 2% does minimal improvement
in hardness for substantial cost. By the 2% level you have gotten the primary benefits of tin which are
lowering the surface tension to improve fill out, and (I think) lowered melting point of the alloy.

When alloys were usually binary, more tin was the way to hardness. But Sb is cheaper and gains
much more hardness, especially if heat treated, for the money.

But, this is my understanding, I not an expert on the alloying of Pb like some here are.
 
Last edited:

Ian

Notorious member
Tin and antimony stick to each other in approximately equal amounts to make what in effect is a single substance within the lead alloy. Excess antimony or tin is "free" within the mix and will precipitate out separately as it cools. Free tin "nodules" contribute to leading and may affect the alloy strength in negative ways. In any event, in a ternary alloy there is absolutely no advantage to having more tin than antimony.
 

fiver

Well-Known Member
short answer.
tin in excess amounts will break away from the SbSn chain and try to form a PbSn chain, only it doesn't do it soon enough in the cooling process.
so what you end up with are Sn nodules surrounded by unbound lead which show up as soft spots in the alloy.
 

CZ93X62

Official forum enigma
I am nothing like a metallurgist, but early in this game I saw that lead alloys (when listed by percentages of included elements) ALWAYS had smaller percentages of tin than of antimony. Lyman #2 was an exception, having the same percentage of tin and antimony (90/5/5). A friend gave me 65# of Ly #2 from Rotometals a few years ago, and that metal casts wonderfully and makes gorgeous bullets--but tin does cost the earth. Linotype is another nice metal to cast with, 4% tin and 12% antimony. Harder than woodpecker lips, too--and for most uses is a waste of the enriching elements.

So--seeing that Folks Who Know What They Are About use smaller percentages of tin than antimony in their bullet alloys, I mimicked their practices and got good outcomes. When in Rome, do as the Romans do. I have been playing around with 40/1, 30/1 and 25/1 lead/tin alloys for revolver and low-pressure rifle bullets (32/20, 38/55, 44/40, 45/70 at BP velocities) and had fun with them. Pretty accurate, and docile recoil. In rifles I used the Ross Seyfried formula--nominal BP weight x 0.4 = charge weight in IMR-4198.
 

Cherokee

Medina, Ohio
In my earlier years (60's to 80's), I strived for Lyman #2 alloy when mixing, Linotype & lead was easy for me to get then, tin came with solder. In more current years I switched to wheel weights until they got harder to find. About 25 years ago I managed to get a great supply of 75% and pure tin real cheap. My main alloy today is 94/3/3 (from lino, lead & tin blending) but I also use 95/3/2 (ww+tin) for low vel loads. Not that much difference between them in my use but 3/3 is better in some loads than 3/2. Having read Glen's comments, I guess I'm in good company for my uses. I have more tin than I'll ever use and need lead to alloy down my large supply of lino. I never messed with lead/tin alloy because I always had plenty of lino.

Fiver - "short answer.
tin in excess amounts will break away from the SbSn chain and try to form a PbSn chain, only it doesn't do it soon enough in the cooling process.
so what you end up with are Sn nodules surrounded by unbound lead which show up as soft spots in the alloy." I think this is what I had in mind in my post #2
 

fiver

Well-Known Member
Ian said pretty much the same thing, I just translated it from engineer to merican.
 

Ian

Notorious member
:rofl:

Hey, I managed to find a layman's way of saying "intermetallic bond", gimme some credit!
 

CZ93X62

Official forum enigma
I think Mr. Seyfried has a RL-15 substitution formula, too, Allen.

That "formula" is for Cordite duplication--OEM Cordite charge weight x 1.15-1.20 using RL-15. I have never ventured into this realm, and have never used RL-15 either.

My mind is a storehouse for useless information, much of the time. Warehouse Of Trivia.

I have used the "4198 x 0.4" bit a whole lot. It works OK in 32/20 and 44/40 revolvers, it leaves behind a few zombie kernels in the bores, but in a SAA that isn't critical. It works WONDERFULLY in rifles, and cleans up the zombies almost entirely--just a few small pieces of powder grit are left. Velocities run about 1275 FPS to 1400 FPS, depending on caliber--25/20 is the fastest, 45/70 is the slowest. No need for gas checks in any of these loads, and the 8.0 x IMR 4198 is the only load that the RCBS 25-85-FN shoots with accuracy from my Marlin 94CL. 25/20 is just plain weird and unpredictable.
 
Last edited: