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What is effect of tin in bullet casting alloys?

Lance
I have several questions pertaining to tin:lead bullet casting alloys in 1:15 or 1:20 ratios.

I specifically omit alloying with antimony or special heat treating of cast bullets.
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1. With no other load or lubricant changes from pure lead bulleted ammunition, does addition of tin to pure lead casting alloy result in more [bullet] metal deposit on ID of barrel, or less?

2. In addition to casting a harder alloy than pure lead, what effect has 1:15 or 1:20 tin:lead alloys on:

A. OD of cast bullet compared with same bullet cast from pure lead?

B. Change in velocity, or change in bullet's ability to accept larger propellant charge, without losing accuracy?

C. Flux used?
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Comments

7 comments

Date Votes
  • Pinhead
    Lance, I don't consider myself to be an "expert" on casting bullets but I have cast bullets and do have some limited knowledge. to answer your questions: 1. The addition of tin in lead to cast bullets is to harden the bulet and make it less likely to lead the inside of the bore-more specifically the grooves. 2A. Most bullet mold manufacturers cut their mold to cast bullets with 1:15 or 1:20 tin to lead mixtures. Molds can be made to drop the bullet in any diameter that you require as long as the manufacturer knows what alloy you will be using-especially the custom mold makers. A mold cut to drop a .429 diameter bullet with a 1:20 alloy will drop a pure lead bullet about .001 or .430 in diameter. 2B. The volocity normally doesn't change with the same powder charge. The thing that will change is that you will be able to drive a tin/lead alloy bullet faster without leading the barrel than a pure lead bullet. That is why we use tin in the lead--to make the bullet harder so that it can resist leading the barrel better.Bullet hardness is desirable up to a point and then a bullet can become so hard as to become fragile. 2C. You need to flux whether you use tin or not. You are fluxing to remove impurities from the metal(lead or tin). The impurities that you want to remove are skimmed off the top of the molten metal and are dull and thicker than the lead or tin. BE CAREFUL-the slick bright colored metal on the top of you melted lead will be melted tin. It melts at a different temperature and is light in weight than lead and floats to the top. Stir the tin back into the lead before fluxing the dross(impurities) off. A really good source for information on casting lead bullets is LYMAN'S CAST BULLET HANDBOOK. If you are going to cast bullets, I would recommend you buy a copy if you can find one. I hope this helps you. Let me know if I can help further.
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  • v35
    To answer your question, addition of tin to the alloy will help the bullet sharply fill the mould.
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  • cussedemgun
    Lance,
    lead alloys for bullet making vary with the purpose intended. pure lead is generally soft enough to strip in the rifling and cause excessive leading as rate of twist & velosity increase. tin added will harden the alloy as will antimony. wheel weights have been used for bullets for many years & in the oldie days we used to add a little more tin to improve casting quality (gives good square edges & uniform weight). tooth paste tubes etc. were the standby source of tin until they went to plastic. if a large amount of alloy is made & kept hot, tin has a tendency to oxidize (burn out) & needs to be replentished. my lyman book #47 says wheelweight metal is 95.5% lead, 0.5% tin, 4% antimony & has a Brinell hardness of 9 (pure lead is 5, & linotype metal is 22 in hardness). linotype mixed 1/2 & 1/2 with pure lead will be about 15 hardness & works well for rifle & mag. pistol. wheelweights with a 1% tin works well for standard vel. pistol bullets.

    it should be noted NEVER, NEVER use battery lead.
    hope this helps, if you still have questions, please re-post. Jim

    "all I really need to know I learned in kindergarten" Robert Fulghum


    anyone who says "nobody needs a full auto" has never been in front of a brown bear charge
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  • cussedemgun
    P. S.
    & one more thing. wheel weight mix with a gas check works well, expands some & does not fowl too bad in Mag. loads. I have used this combo. (with a gas check) up to 2000 f.p.s. with good results.

    "all I really need to know I learned in kindergarten" Robert Fulghum


    anyone who says "nobody needs a full auto" has never been in front of a brown bear charge
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  • TaiChi
    I have cast bullets with 50/50 bar solder. They come out of the mold with sharp edges, keep their shape when shot thru phone books but cast about 5% lighter then a standard alloy. Is there a problem using this lead mixture?

    Steve
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  • cussedemgun
    TaiChi;
    bar solder (50/50 tin & lead) is a convenient sorce of tin for alloying, but rather more expensive than scrap lead. try mixing
    20 pounds wheel weights with one pound bar solder. this mix comes out near "lyman #2" in hardness & castability (Brinell hardness
    12-14)

    "all I really need to know I learned in kindergarten" Robert Fulghum


    anyone who says "nobody needs a full auto" has never been in front of a brown bear charge
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  • Xracer
    Antimony increases the hardness of a lead alloy. Tin adds little hardness, but increases the temperature range over which lead or a lead alloy will cast well.

    Linotype metal is ideal for casting bullets, but, what with modern printing methods, is becoming increasingly difficult to find.

    Wheelweights are cheap, readily available, and make excellent bullets, but...cast well over a relatively narrow temperature range. The addition of 1%-2% tin, increases the temp. range considerably.
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