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Thread: Penetration of a Sphere formula?

  1. #31
    Quote Originally Posted by Jim Watson View Post
    I don't know about zinc buckshot but the old American Rifleman found that a zinc .30-06 would penetrate as much wood as GI AP. One tester found zinc .38s beating up his bullet trap.
    ZAMAK 3 is comparable in hardness to brass, so I'm not surprised it shows superior penetration to typical FMJ.

    I'm kind of curious how it would do as a reduced recoil .38 / .357 load for ultra lights like the S&W 340. Z3 is 0.58 the density of lead, so a 150gr Lead Wadcutter would be 87gr cast from Z3.

    At 1000fps from a J frame (power factor 87) you'd get tolerable recoil, a wadcutter that would not deform and lose its sharp edge when impacting bone, and the overall light weight would likely keep penetration depth in the ideal 12-18" zone.

    You'd also save 0.81oz of weapon weight with the 87gr Zinc wadcuters in a 5 shot j frame Vs 158gr LSWC, making the 340 that much lighter to carry.

  2. #32
    Quote Originally Posted by spyderco monkey View Post
    ZAMAK 3 is comparable in hardness to brass, so I'm not surprised it shows superior penetration to typical FMJ.

    I'm kind of curious how it would do as a reduced recoil .38 / .357 load for ultra lights like the S&W 340. Z3 is 0.58 the density of lead, so a 150gr Lead Wadcutter would be 87gr cast from Z3.

    At 1000fps from a J frame (power factor 87) you'd get tolerable recoil, a wadcutter that would not deform and lose its sharp edge when impacting bone, and the overall light weight would likely keep penetration depth in the ideal 12-18" zone.

    You'd also save 0.81oz of weapon weight with the 87gr Zinc wadcuters in a 5 shot j frame Vs 158gr LSWC, making the 340 that much lighter to carry.
    That's an interesting idea, especially if you could guarantee—through proper propellant selection—that a wadcutter made Zamak 3 would reliably produce a muzzle velocity of 1,000 fps.

    According to this source, the density of Zamak 3 alloy is 6.6 grams/cm3:

    http://www.matweb.com/search/DataShe...0a2bc79&ckck=1

    The density of Lyman's No. 2 hard-cast 5% antimonial alloy is 10.80 grams/cm3:

    http://www.matweb.com/search/DataShe...10b872dd61923e

    This suggests that a 148-grain .38-caliber wadcutter, if cast from Zamak 3, sized at 0.3575'' would drop from the mould with a mass of 90.45 grains.

    With a muzzle velocity of 1,000 fps, the predicted penetration of a 0.3575'' 90.45 grain wadcutter in soft tissue would be—

    Q-model: 12.93 inches
    mTHOR model: 14.61 inches
    MacPherson WTI model: 15.32 inches

    The compressive yield strength of 5% antimonial lead alloy is 24.5 MPa as opposed to 415 MPa for the Zamak 3 alloy which should make the Zamak wadcutter much less likely than its lead counterpart to deformation against hard tissues like bone. At 1,000 fps, a strike against bone would result in a pressure on the order of 100 MPa, so it is probable that the Zamak projectile would not deform upon striking bone.
    ''Politics is for the present, but an equation is for eternity.'' ―Albert Einstein

    Full disclosure per the Pistol-Forum CoC: I am the author of Quantitative Ammunition Selection.

  3. #33
    Quote Originally Posted by the Schwartz View Post
    That's an interesting idea, especially if you could guarantee—through proper propellant selection—that a wadcutter made Zamak 3 would reliably produce a muzzle velocity of 1,000 fps.

    According to this source, the density of Zamak 3 alloy is 6.6 grams/cm3:

    http://www.matweb.com/search/DataShe...0a2bc79&ckck=1

    The density of Lyman's No. 2 hard-cast 5% antimonial alloy is 10.80 grams/cm3:

    http://www.matweb.com/search/DataShe...10b872dd61923e

    This suggests that a 148-grain .38-caliber wadcutter, if cast from Zamak 3, sized at 0.3575'' would drop from the mould with a mass of 90.45 grains.

    With a muzzle velocity of 1,000 fps, the predicted penetration of a 0.3575'' 90.45 grain wadcutter in soft tissue would be—

    Q-model: 12.93 inches
    mTHOR model: 14.61 inches
    MacPherson WTI model: 15.32 inches

    The compressive yield strength of 5% antimonial lead alloy is 24.5 MPa as opposed to 415 MPa for the Zamak 3 alloy which should make the Zamak wadcutter much less likely than its lead counterpart to deformation against hard tissues like bone. At 1,000 fps, a strike against bone would result in a pressure on the order of 100 MPa, so it is probable that the Zamak projectile would not deform upon striking bone.
    Thank you for running the numbers! That looks very promising.

    Super Vel is getting 1250fps from a 90gr .38 +P out of a J frame, so 1000fps shouldn't be an issue. Quickload would be able to figure out the right powder charge pretty easily.

    Zinc/ZAMAK is also cheap ($3.75lb), and can be gravity cast similar to lead, so a lead bullet company could retool their casting machines relatively easily for zinc. 1lb of lead would make 47x 148gr lead wadcutters; 1lb Z3 produces 77x 90gr Zinc wadcutters. So overall projectile cost would likely be similar to hardcast lead, especially as the Z3 does not need gas checks or powder coating.



    This would result in a much cheaper projectile then some of the solid copper offerings that are available, such as the lehigh XD.

    In terms of non-deformation after hitting bone, this result seems to validate that:


    http://castboolits.gunloads.com/show...esting-results

    All in all I think the 90gr Zinc Wadcutter it could be a pretty solid snubbie load.

  4. #34
    Quote Originally Posted by spyderco monkey View Post
    Thank you for running the numbers! That looks very promising.

    Super Vel is getting 1250fps from a 90gr .38 +P out of a J frame, so 1000fps shouldn't be an issue. Quickload would be able to figure out the right powder charge pretty easily.

    Zinc/ZAMAK is also cheap ($3.75lb), and can be gravity cast similar to lead, so a lead bullet company could retool their casting machines relatively easily for zinc. 1lb of lead would make 47x 148gr lead wadcutters; 1lb Z3 produces 77x 90gr Zinc wadcutters. So overall projectile cost would likely be similar to hardcast lead, especially as the Z3 does not need gas checks or powder coating.



    This would result in a much cheaper projectile then some of the solid copper offerings that are available, such as the lehigh XD.

    In terms of non-deformation after hitting bone, this result seems to validate that:


    http://castboolits.gunloads.com/show...esting-results

    All in all I think the 90gr Zinc Wadcutter it could be a pretty solid snubbie load.
    That's an interesting experiment, but not quite as close to an impact on bone as one might be led to believe.

    The density of pine—assuming a typical unseasoned Northern White Pine specimen with a moisture content of ≈10%—is about 0.577 g/cm3 whereas cortical bone averages about 1.850 g/cm3, which is about 3 times more than that of the Northern White Pine. Using the Bernoulli pressure equation [P = ˝ρV2] to compute peak pressure at an impact velocity of 1,000 fps gives us 26.8MPa in pine as opposed to 85.9MPa in bone which is over three times the pressure that likely occurred in the experiment above. In any event, if I was pursuing this beyond the theoretical bounds of this discussion, I would likely select this cortical bone simulant as a ''worst case'' test bed—

    http://www.matweb.com/search/DataShe...5df5e9d9171da9

    —and accept the theoretical as being ''verified'' if no deformation of the Zamak 3 alloy wadcutters occurred at 1,100 fps (115.8MPa) against that simulant.

    As for unforeseen detrimental issues, I suppose that possible barrel wear issues could be investigated by running a few tens of thousands of the Zamak 3 bullets down a ''sacrificial'' barrel checking for unusual or extreme wear every 1,000-round interval with an air-gauge micrometer.

    Aside from the cost reduction of zinc alloys, I wonder why it never caught on with the major manufacturers. Perhaps there is some difficulty associated with gravity-cast eutectic zinc alloys that I am unaware of that makes the option unattractive to the major ammunition manufacturers especially as good self-defense ammunition has lately become so scarce and expensive?
    Last edited by the Schwartz; 12-26-2020 at 03:04 PM.
    ''Politics is for the present, but an equation is for eternity.'' ―Albert Einstein

    Full disclosure per the Pistol-Forum CoC: I am the author of Quantitative Ammunition Selection.

  5. #35
    Quote Originally Posted by the Schwartz View Post
    ...
    —and accept the theoretical as being ''verified'' if no deformation of the Zamak 3 alloy wadcutters occurred at 1,100 fps (115.8MPa) against that simulant.

    As for unforeseen detrimental issues, I suppose that possible barrel wear issues could be investigated by running a few tens of thousands of the Zamak 3 bullets down a ''sacrificial'' barrel checking for unusual or extreme wear every 1,000-round interval with an air-gauge micrometer.

    Aside from the cost reduction of zinc alloys, I wonder why it never caught on with the major manufacturers. Perhaps there is some difficulty associated with gravity-cast eutectic zinc alloys that I am unaware of that makes the option unattractive to the major ammunition manufacturers especially as good self-defense ammunition has lately become so scarce and expensive?
    That would be a nice test, thats good to know there is now good bone simulant for ballistic testing; a step up from slapping some pork ribs in front of the gel.

    In terms of Zinc ammunition, it has been and is currently made:







    The problem there is that all of these are designed as lead free training ammunition. This is decidedly un-sexy - only appealing to those poor few not allowed to fire lead.

    As of yet, there has only been one defensive Zinc bullet - the Aguila IQ. This was a sort of Triton Quick Shock meets Liberty Civil Defense type lightweight, high velocity fragmenting bullet.



    Like other fragmenting bullets, it had poor penetration. Then on top of that, the high velocity plus hardness of zinc allowed it to penetrate some of the older Level II vests used at the time (15 years ago) which killed the sale of it.

    Where Zinc would shine today is with special applications:
    -Low recoil .38 wadcutter
    -Lehigh XD style fluted, high velocity monolithic solids (cheaper then copper, even higher velocity)
    -Low recoil and or high pellet 00 buckshot (ie 00 12 pellet low recoil zinc)
    -6mm and 6.5mm Creedmoore VLD high velocity, low cost target ammo (like Warner Flatline, but zinc, so 20 cents instead of $1 per projectile). The ultra low drag shape would help make up for the reduction in BC of the lighter weight, and would also allow for much higher velocity for flatter trajectory.



    In terms of manufacturing, a major manufacturer (Federal, Hornady, etc) would use proper Zinc diecasting equipment, which injects molten zinc at pressure. This is whats used for diecast parts like Zippers and doorknobs etc, and produces parts with superior precision and comparable speed to plastic injection moulding.

    Gravity casting is more for the small shops that currently make hardcast lead bullets - who are more likely to take up the Zinc wadcutter project.

  6. #36
    That last reminds me of the 7.92 CETME with aluminum core.

    There was briefly a frangible training bullet made of a stranded zinc cable in a jacket. It was meant to just kind of unravel against a gong.

    Friction of zinc on steel leaves a protective coating similar to Sheradizing. This was the idea of the Harvey Pro Tex Bore bullets with zinc washer base.
    https://hawkbullets.com/prot-x-bore.html
    Code Name: JET STREAM

  7. #37
    Quote Originally Posted by Jim Watson View Post
    That last reminds me of the 7.92 CETME with aluminum core.
    Yes, very similar concept.

    Also similar to the 5.56x38 FABRL, which used a 37gr but very low drag projectile to match 5.56x45 55gr ballistics.

    https://www.thefirearmblog.com/blog/...5-56x38-fabrl/



    For 6.5 Creedmoor, that 123gr Warner Faltline would be 90gr in Zamak 3, clock around 3200fps, and have a BC higher then a typical 108gr 6.5 due to the extremely low drag shape. So probably a pretty awesome 0-600yd target round.

    But it wouldnt work with 5.56 or .308, as those cases don't have enough ogive room for those types of very low drag, long bullets. Thats why the 5.56 FARBL was shortened from 45mm to 38mm.

    So once again a pretty niche application, which explains why we haven't seen the major manufacturers pursuing it.

  8. #38
    It would be interesting to see somebody exploit that niche instead of the next 6.5mm Trivial Variant Mk III.
    Code Name: JET STREAM

  9. #39
    Quote Originally Posted by Jim Watson View Post
    Friction of zinc on steel leaves a protective coating similar to Sheradizing. This was the idea of the Harvey Pro Tex Bore bullets with zinc washer base.
    https://hawkbullets.com/prot-x-bore.html
    I am surprised that a major manufacturer has not seen fit to capitalize on the protective qualities of zinc residue left behind by zinc bullets much like Remington did with the lead styphnate in their primers which provided some measure of protection against corrosion in the bores of uncleaned firearms. Considering that zinc has a lot going for it (reasonable hardness in 82HBN as opposed to the hardness of Lyman #2 at 16HBN, relative expense, protective qualities, and adequate mass-density) in addition to the fact that it does not pose the threat that a ''heavy metal" like lead does in terms of carcinogenicity and teratogenic, it seems almost an ideal option.
    ''Politics is for the present, but an equation is for eternity.'' ―Albert Einstein

    Full disclosure per the Pistol-Forum CoC: I am the author of Quantitative Ammunition Selection.

  10. #40
    Quote Originally Posted by the Schwartz View Post
    I am surprised that a major manufacturer has not seen fit to capitalize on the protective qualities of zinc residue left behind by zinc bullets much like Remington did with the lead styphnate in their primers which provided some measure of protection against corrosion in the bores of uncleaned firearms. Considering that zinc has a lot going for it (reasonable hardness in 82HBN as opposed to the hardness of Lyman #2 at 16HBN, relative expense, protective qualities, and adequate mass-density) in addition to the fact that it does not pose the threat that a ''heavy metal" like lead does in terms of carcinogenicity and teratogenic, it seems almost an ideal option.
    I think its the qualities we like about Zinc for .38 wadcutter and other niche applications - low weight, low recoil, high velocity, high resistance to deformation - make it unattractive for most major ammunition applications.

    -Low weight = poor BC's for most rifle calibers (except 6.5 creedmoor and grendel, 6mm ARC and creedmoor, and .300blk)

    -Low recoil = poor training ammunition for handguns, as it will have less recoil then traditional lead JHP's

    -High velocity = different point of impact then traditional lead projectiles

    -Resistance to deformation = cannot be used for expanding rifle or handgun ammo for hunting and self defense. May also be unsafe for training on steel targets (bullet may ricochet rather then shatter.)

    Most of the major ammunition makers are pretty conservative - most majors don't even offer solid copper ammo - so I'm not really surprised none have pursued exotic Zinc niche loads.

    But I do see it as a promising avenue for a Lehigh / Underwood / etc small outfit, as well as a bullet maker to offer for reloading projectiles.

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