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Thread: Zinc bullets, why harder on bore than copper?

  1. #1
    Boolit Master jabilli's Avatar
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    Zinc bullets, why harder on bore than copper?

    So I'm a bit confused-

    I understand that a well designed bullet will deform upon having the heat and pressure from the expanding gas of the cartridges charge...This deforming will better seal the bullet to the bore and will allow less blowby- minimizing gas cutting. The bullet, or gas check, has to be soft enough to allow for this.

    I also understand bullets with a full metal jacket do not expand in this manner, but rather are made to more extreme (tight) tolerances.

    I was looking into using zinc for cast .223 as lead simply dissipates at any kind of speed, even with a gas check, and full metal jackets require swaging equipment.

    My point of confusion is, I'm told zinc will wear a barrel very quickly... I look at the brinell hardness of zinc and it is in the realm of 400... I look at the hardness of copper and it is around 800... I don't disbelieve the experienced, I'm just confused as to why?
    I believe you...but my Tommy gun don't.

  2. #2
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    If you can keep your mold hot enough to get good boolits, you then need to think about load data for the odd weights. Where would you get load data. Also, I don't think the zinc would grip the rifling to shoot straight.
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  3. #3
    Boolit Master

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    Not sure who told you that zinc would wear a barrel faster than copper but I am with you and think that is incorrect. There were boolits made that incorporated zinc "washers" essentially attached to the base of the boolit. These were called Pro-Tex:

    http://castboolits.gunloads.com/show...c-driving-band

    I see a few threads on them on various sites but no current availability. I don't think they did much of anything better than gas checks.

    Corbin swaging offers a similar idea but for swaging copper discs onto boolit bases.

    There are various grades of zinc/zinc alloy and some like Zamac/Zamak are used as bearing materials so these definitely would not wear steel any faster than copper. In fact I doubt a boolit made of zinc or any typical alloy would be a problem that way. the bigger issue is making zinc boolits. While some have tried it, I think it would be easier to machine zinc bullets the way the solid brass/bronze bullets are made than to cast it.

    That's my take anyway.

    Longbow

  4. #4
    Boolit Master dakotashooter2's Avatar
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    I've often wondered if injection molding would be the best option for zinc. Seems it would produce a more consistent bullet with less voids.

  5. #5
    Boolit Master
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    Quote Originally Posted by dakotashooter2 View Post
    I've often wondered if injection molding would be the best option for zinc. Seems it would produce a more consistent bullet with less voids.
    They call it die casting when it's done with metal, but that's how many zinc items (drawer pulls, car door handles, lamp bases, and little bitty model cars) are made. Die casting should be able to produce large quantities of accurately dimensioned zinc boolits quickly, but what we do (casting in a mold) is exactly that, minus the sprue of dozens of parts all cast in a single shot.

    Use an iron mold; zinc will bond to aluminum or brass. Cast hotter than you would with lead, and segregate your equipment so you never use lead with your zinc equipment or zinc with your lead stuff. Zinc bullets will work fine; they've been sold commercially, and in fact there are lead-free .22 LR rounds in current production that use zinc bullets.

    You will probably want your zinc bullets a tiny bit smaller than lead for the same gun -- instead of one or two thousandths over groove, zinc should be at or a thousandth under groove diameter, generally. Zinc will not work well in applications that depend on the bullet upsetting to fill an oversize bore (say, a .32 or .38 Long Colt in a revolver originally made for the old style heeled bullet rounds, but loaded with inside lubed bullets, or a Webley Mk. IV made for hollow base) but in most conventional rounds and guns made today, correctly sized zinc bullets will work fine.

    As for loading data, use minimum starting loads for jacketed bullets the same weight, and work up carefully. Zinc will have less barrel friction than jacket metal, so you should get lower pressure than the same weight jacketed bullet in spite of the longer bearing area due to the lower density of the zinc.

  6. #6
    Boolit Master rsrocket1's Avatar
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    Wow, this might be the way of the future. If lead becomes illegal, at least we would be able to shoot with zinc bullets. But I suppose there would be some anti-gun environmentalist that will say zinc is toxic to condors too (especially if you feed it to them at 2750 fps).

  7. #7
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    in the late 50's a company called jugular made and sold zinc bullets.
    they are much lighter than lead so they require much higher velocity's to poke holes in things.
    look back at all the trouble the duck hunters had/have with steel shot.
    you have to speed steel shot up for it to penetrate,but it's light so it slows right down again.
    so you make it bigger to carry more weight.
    the bigger frontal area makes penetration harder.
    so you speed it up again,,, oops you can't you run out of room for more powder.
    it's all an educated guess,,,, till the trigger is pulled.

    the more i find out about shootin boolits, the more it contradicts everything i ever learned about shooting jaxketed.

  8. #8
    Boolit Master fredj338's Avatar
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    Well zinc is certainyl softer than solid bronze or solid copper, so it's not that just getting the zinc to cast well is the bigger issue I would think. I know what zinc does to a lead alloy & makes getting good castings difficult. A smaller bullet like a 224 is making things even more so. If you can get it to mold, I see no harm coming to the barrel.
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  9. #9
    Boolit Master
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    I don't know where you get your information but industry standards for Zamak #3, the most widely used alloy in North America, is BHN 82. Common recommendation for zinc alloy bullets is .001 over groove diameter. I take that to be a minimum of .001 inch as zinc is probably going to show very little if any expansion at acceptable pressures.

    If one follows good loading practice and starts low and gradually increases load that will take care of different engraving forces due to bullet hardness. Once bullet is engraved there should not be any pressure differences. Zinc is so much softer than steel than wear due to friction should not be a problem. Army and Navy ordnance has used zinc projectiles for proof testing artillery for generations. I doubt they would risk damage to such valuable and expensive pieces if there was an increased risk.

    It has been shown that jacketed rifle bullets with pure lead cores create higher pressures than ones with hardened lead cores.

  10. #10
    Boolit Master
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    Bigger frontal area of birdshot does not make penetration harder. As the shot becomes larger diameter it also becomes longer increasing sectional density. On 'soft' targets momentum density is the primary determinant of penetration.

  11. #11
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    untill you make it light for it's frontal area.
    it's all an educated guess,,,, till the trigger is pulled.

    the more i find out about shootin boolits, the more it contradicts everything i ever learned about shooting jaxketed.

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    so, is zinc oxide harmful?
    Sometimes you have to ignore the "good idea fairy"

    Please stop telling me "That can't be done" while I'm doing it, it's just plain annoying.

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  13. #13
    Boolit Master popper's Avatar
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    I would think solid zinc would be like solid copper and increase wear, who knows how much. Jacketed just displaces the lead core. Pressure on lands of compressing solid metal is much greater. Obviously is does work, but the question was about wear.

  14. #14
    Boolit Master Thompsoncustom's Avatar
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    Casting zinc is a lot easier than you might think. Here's is a pic of a zinc/alum bullet I cast and shined.
    Click image for larger version. 

Name:	ShowBrass.jpg 
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ID:	59649

    I cast all my zinc in a plain Lee mold as I didn't want to mess up an steel ones. They do produce bullets that are a lot lighter tho, My lee 125gr mold throws 80gr zinc/alum bullets and my 102gr mold throws 60gr bullets. It's been about a year since I have cast any of these tho I just bought a mold the other day that I'm going to be playing with, already removed the lube groove but still have plenty of work to do.

  15. #15
    Boolit Master


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    Please stop it. This is enough. Everytime I turn around there is something new one of you guys is doing and I end up having to do it. I spend so much time and money on new casting equipment and processes I never get out to the range anymore.
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    Boolit Designer 45 2.1's Avatar
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    Quote Originally Posted by 500MAG View Post
    Please stop it. This is enough. Everytime I turn around there is something new one of you guys is doing and I end up having to do it.
    Actually, most all of this is old technology. Most all these supposedly new ideas here have been done several times before... and written about.
    45 2.1

    Knowledge without understanding is a dangerous thing. For a little knowledge entices us to walk its path, a bit more provides the foundation on which we take our stand, and a sufficient amount can erect a wall of knowledge around us, trapping us in our own ignorance.

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    Knowledge is easy to get, but worthless if you never use it. However the info is free, so the only person you have to blame is yourself if you chose not to use the information.

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    Quote Originally Posted by Thompsoncustom View Post
    Click image for larger version. 

Name:	ShowBrass.jpg 
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    That's just really pretty.
    Sometimes you have to ignore the "good idea fairy"

    Please stop telling me "That can't be done" while I'm doing it, it's just plain annoying.

    HOW to order GC's and any other questions go here:
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  18. #18
    Boolit Master
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    Quote Originally Posted by BAGTIC View Post
    I don't know where you get your information but industry standards for Zamak #3, the most widely used alloy in North America, is BHN 82.
    Sure. But pure zinc is around BHN 30-32, as I recall -- similar hardness to some of the harder lead alloys we use.

  19. #19
    Boolit Master
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    A larger diameter sphere will always be heavier than a smaller one made of the same material.

  20. #20
    Boolit Master
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    Soft iron and sintered iron driving bands for artillery projectiles were introduced at least as long ago as WW2 and are used by many counties today. At one time Norma produced steel jacketed hunting bullets and of course almost all military 7.62x39 mm ammo has steel jackets. If steel doesn't wear them out why should zinc?

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BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
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