Does adding Tin or Antimony?

[ACC]

Does adding Tin or Antimony increase or decrease the molded diameter of cast boolits. I have mixed up some high Tin casting Lead and all my boolits come out of the mold at least .003 larger than the mold cavities.

ACC

[dondiego]

Does adding Tin or Antimony increase or decrease the molded diameter of cast boolits. I have mixed up some high Tin casting Lead and all my boolits come out of the mold at least .003 larger than the mold cavities.

ACC
I think that you might have answered your own question. Alloys tend to cast larger than lead and antimony alloys for sure do so. However, many mold makers take the alloy into consideration and cut the molds based on the alloy stated to be used.

[Bazoo]

Both tin and antimony cause an increase in diameter, but the increase isn't much less with tin than it is with antimony. Pure lead produces the smallest diameter.

[BK7saum]

0.003" larger than the mold cavities themselves or 0.003" larger than boolits cast from pure lead or a low tin alloy?

I don't see how a boolit can be larger than the cavity it was cast in. Are you using Cerrosafe for a casting alloy?

[kevin c]

ACC’s alloy surely gives a bullet that shrinks to under the mold cavity diameter, but perhaps the mold maker’s alloy shrinks .003” more, so maybe ACC means .003” bigger than the advertised nominal cast diameter?

[Winger Ed.]

Lyman #2 is the benchmark.
It is what the mold makers use to determine the size and weight of dropped boolits.
Any variation from that recipe gives different size & weights.

For example:
I cast a much softer boolit out of a .45 405 gr. Iron mold. Mine come out at 424gr.

[Rapier]

+1 Tin added to pure lead assists with achieving a consistent 100% fill of the cavity.The bullets cast with tin, cast larger than bullets cast with pure lead because of the cavity fill out, only. The effect of adding tin levels off at higher % of tin and 2% is about the biggest bang for the buck in that alloy process of lead and tin alloy only. Truly a process of demising return, to keep adding tin by percentage. To get better consistency, more hardness, more velocity, etc., you can add antimony and arsenic to the lead/tin alloy.

[Bazoo]

Lyman #2 is the benchmark.
It is what the mold makers use to determine the size and weight of dropped boolits.
Any variation from that recipe gives different size & weights.

For example:
I cast a much softer boolit out of a .45 405 gr. Iron mold. Mine come out at 424gr.

I very rarely disagree with you sir, but it is only Lyman that regulates their moulds to Lyman #2.

RCBS Regulates theirs: Rifle bullets = linotype, pistol bullets = 10:1, cowboy bullets = 20:1.

NOE regulates theirs for Wheel weight alloy.

[Winger Ed.]

Opps.
I never could find exactly what RCBS uses, but just figured they went along with the program Lyman had established.

Thanks for pointing that out. .... I learn something new every day.

[Gobeyond]

Lead shrinks when it cools. Tin and antimony don’t. The more of them you use the less shrinkage you have and better fill out.

[kevin c]

…bullets cast with tin, cast larger than bullets cast with pure lead because of the cavity fill out, only...

I thought it was just a less dense alloy than pure lead?

Certainly I’ve read the rest is true: better fill out, which tops out at around 2% Sn, and better hardening effect (and cheaper to boot) from Sb and As than Sn. And I’ve also heard that Lyman #2, at 5% each Sn and Sb is favored not only for its hardness, but also its ductility, a result of the amount of balanced Sb/Sn in the alloy, so tin over 2% is useful in some situations.

[fredj338]

Molds are designed around a specific alloy. Going more lead or more tin will change weight & as cast size.

[fredj338]

Lead shrinks when it cools. Tin and antimony don’t. The more of them you use the less shrinkage you have and better fill out.

Well they do, just at a diff rate.

[Gobeyond]

Well they do, just at a diff rate.
Ok thanks, gotcha.

[avogunner]

I believe this subject is exactly why casters often complain about molds throwing too small of boolits. I prefer Lyman#2 (at least my alloy version of it) for all rifle shooting. Is it necessary, no but just my preference. Anyway, I often (and usually cheap) will pick up molds that the previous owner says "casts too small". Most of the time, they are just fine with a harder alloy.
Semper Fi