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  1. #1
    Cryotech is offline Junior Member
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    Bullet Damage Formula?

    Hello, new here and nice to meet you all

    I realize this is a handgun forum, but I was hoping someone here would know what I'm talking about since you're the experts in this particular field.

    I develop games and am currently in the process of developing two games that require the calculation of bullet damage but I'm not sure how to properly do this based on the ballistics type of firearm used (pistol, rifle, shotgun etc.) to ensure it's realistic in-game. I've tried searching for this information online but was unable to find what I needed. Too be honest, I'm not exactly sure what I should be looking for formula wise.

    If anyone here could help me, I would be extremely grateful for the help!

  2. #2
    buckler's Avatar
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    nobody has the answer that you seek, sorry. If anyone did, about 90% of the defensive handgun and ammo market would quickly disappear, because so much of it is based upon nothing more than "hype".

  3. #3
    MLB's Avatar
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    Complicated stuff in real life. For a gaming scenario, I'd think that muzzle energy would be a good place to start to reasonably scale one projectile to another. You can find this info at any of the manufacturer's websites.

  4. #4
    buckler's Avatar
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    General Hatcher had a formula in his "Notebook", but it was based upon lies

    that LaGuarde put out about his and Thompson's "test" on a lousy 6 steers back in 1909, or thereabouts, which proved exactly nothing. The entire test was published in the 1981, or 82, I forget, Gun Digest, and it was a complete joke. So what the "computer man" RII test of the 1970's. Garbage in and garbage out, as they say. flawed testing means, and or flawed presumptions/protocols naturally lead to bs results. If .45 military "ball" fmj (full metal jacket) ammo was anywhere close to being as "effective" as all the war stories would have us believe, an alley cat couldn't run off with one thru his chest, but they do, routinely, you can prove it for yourself. Ditto coons, chucks, jackrabbits, nutria, armadillos, opposums, many vermin type critters that you can easily hit with a handgun, if you try. But nobody wants to go to that much trouble, it seems. I am certain that the reason that they don't do so is they don't want to know the truth. Low velocity, heavy for the caliber jhp's don't expand much, or reliably, in flesh. It is that simple. You need at least 1000 fps in a .45, and 1200 fps in 9mm.

  5. #5
    Cryotech is offline Junior Member
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    Thanks for the replies,

    @Buckler - I understand what you're getting at but 'purely accurate results' isn't what I'm looking for. Though if those did exist, I would be one happy camper lol. What I'm looking for is the generalized formulas used in ballistic testing, which I do know exist because I've seen them, but I just don't know where to find them. If they didn't exist, we game developers would have nothing to go on to make the damage as realistic as possible in-game. I realize there's many factors and variables and I will never truly accomplish a true-to-life conversion, I just want to achieve as realistic statistical damage as possible which will require tweaking on the backend to accomplish the actual physics of it engine wise. That's why all I really need is just a basic formula that is 'generally' used to calculate ballistic damage.

    You're statement about 1000 fps in a .45 and 1200 fps in 9mm is heading down that right direction. What is the formula you use to figure this out when trying to calculate bullet damage?

    @MLB - Thanks for the info, I found some information regarding muzzle energy but I'm at a loss on how it factors into the equation. I've tried experimenting, but can't figure it out. I'll keep searching until I find an actual formula regards of how generalized it is.

  6. #6
    buckler's Avatar
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    some baloney claiming to do what you say probably do exist, but in reality, there is no way to know. Many men have continued to fight or flee after being hit with very powerful (momentum or energy) large caliber loads, so while you might up the odds of getting a stop with a powerful load, it's nothing like a formulaic thing. It's mostlly a luck thing, especiallly with loads less powerful than the famed 125 gr, full power jhp 357, from a 4" or longer barrel. The .44 mag has failed to stop men, the 12 ga slug and buckshot has failed to stop men, with close range chest hits. 3006, 7.7 Jap, and 8x57 and 7x57 ball failed to stop many men. Because so many millions of men were shot with such loads a 5% failure rate is still many 10's of thousands of men who were not stopped. Sure, they died later, but they did not drop to the shot, as so many of the ignorant are convinced always happens with such rifle loads.

  7. #7
    Cryotech is offline Junior Member
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    @buckler - True, there is no "absolute" way to know and this I realize, but there is generalized formulas used to calculate the potential damage a gun could cause. These numbers are then pumped into the game engine and the physics are tweak to attempt to obtain a more realistic feel.

    Of course some people drop where they stand or flee or fight, and it all depends on the type of gun used, bullet used, shot location and yes, luck. But that's not what I'm looking for because I don't care about that aspect of the formula. I can convert that by adding my own specs. Again, what I want is a number I can work with.

    What I'm looking for or asking if anyone knows about, is any formula that ballistic testers use to calculate the potential regardless if it's baloney or not. That's what I'm looking for and I know those exist.

  8. #8
    MLB's Avatar
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    Hello Cryotech. The muzzle energy is the product of the velocity (at the muzzle) and the bullet mass.

  9. #9
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    Oh boy! Buckler has certainly put his foot into it now! He's set himself up to say that Hatcher, and Thompson and LaGarde, were peddling bull dung. How very interesting!

    Tell me, Buckler, just how many animals have you killed and dissected, to arrive at your conclusions?
    Exactly none. I'm certain of it.

    Instead of reading a "digest" of what they wrote, have you ever read their original work?
    No, I didn't think so.

    I strongly suggest that you stop giving advice on subjects about which you so very obviously know nothing.
    Either do some real experimental work, or, at least, read the original writings you wish to condemn.
    Then gain some real shooting experience.
    Only then should you seek to advise the rest of us.

  10. #10
    Steve M1911A1's Avatar
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    MLB has set you on the right track, Cryotech.

    Along with muzzle energy, you might wish to figure-in terminal energy at the distance at which a given hit was made. These figures are available from ammunition-manufacturers' web sites, usually as muzzle- and distance-related tables. Particularly useful might be Remington, Winchester, Hornady, and Norma. Also look up the ammunition tables in the Gun Digest, if they're available on-line.

    The concept is further complicated by the construction of the particular bullet. Some bullets do not appreciably expand, and some expand to much more than double the original diameter. Some almost explode within flesh or other semi-fluids.

    So each calculation of "bullet damage" could conceivably include bullet velocity at the moment of contact, original bullet diameter, expanded bullet diameter, and bullet mass.

    Did that help?

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    Quote Originally Posted by Cryotech View Post
    I develop games and am currently in the process of developing two games that require the calculation of bullet damage but I'm not sure how to properly do this based on the ballistics type of firearm used (pistol, rifle, shotgun etc.) to ensure it's realistic in-game.
    Yep, the guys are correct. You have stepped squarely into a old and continous and bitterly fought controversy on how to evaluate calibers and ammo "stopping power".
    "Big and slow (say .45 ACP) or "Small and fast (say 9mm +P).
    This will go on forever. It can't be done "correctly". WAY too many variables.

    But, you want a simple algorithm to plug numbers in to "separate" weapon lethality.
    No problem. If you don't need to make it match the real world.

    Here is a long table of Dexter's Table of Hatcher's "work". Done in the '30's. Yes, it's rather old. And, discredited.
    Hatcher's formula is discredited. Dexter's table of results is fairly current, and calculates Hatcher's formula correctly.

    At the top is how Hatcher calculated the data for various calibers and stuff. And then a long table of
    calculated "data". Here is the "header" at the top of Dexter's Table of Hatcher values.

    The Hatcher Formula is an attempt to mathematically evaluate the approximate effectiveness of pistol ammunition at incapacitating a person.
    Developed by Gen. Julian Hatcher in the 1930's, it uses the bullet momentum, frontal area, velocity, and a 'form factor.'
    The formula is:
    RSP = M * A * F
    where RSP = Relative Stopping Power Index, M = Momentum of the bullet in foot pounds, A = Area of the bullet in square inches,
    F = Form factor derived from his observations with some additions for later bullet types. The table lists an RSP for each 'Form Factor',
    whether or not that form of bullet actually exists for a particular caliber or weight. The form factors presented below include:

    0.70 Fully Jacketed Pointed
    0.90 Fully Jacketed Round Nose
    1.05 Fully Jacketed Flat Point
    1.10 Fully Jacketed Flat Point (Large flat)

    Hatcher's Theory Of Relative Stopping Power

    If you've made it this far, I'll go you one better. Here is a "Hatcher data calculator" which allows the input raw data
    (which you can get from the Dexter Table) and takes care of all the conversion factors necessary to to get the output in proper units.
    Stopping Power Calculator

    From these two items, you can reverse engineer your algorithm, needing only a "few" look-up tables.

    This takes care of "handguns". For "larger" weapons, just get input data for rifles and shotguns.
    A good source is the ammo section of Midway USA. Just select a few "representative" rifle and shotgun "loads".
    Ammunition - Shop Premium & Discount Ammunition at MidwayUSA

    All this is almost completely bogus in terms of predicted performance in the real world.

    But, not to worry. You are after a "mildly logical algorithm" which has a shot (pun intended)
    at separating "weapon performance" on some human or alien or whatever.

    You have enough "meat" here to at least start that job, I think. Good Luck !

    Oh yeah, plain old physics.
    Momentum MV= Mass (M) x Velocity (V)
    Area A = Pi x Diameter (D) x Diameter (D) that is, D squared. Pi =22/7. For us, 3.14159265 is close enough.

    Kinetic Energy KE = Mass (M) x Velocity (V) x Velocity (V) that is, Velocity Squared.
    KE is often used as a crude indicator of a cartridge's "go-power".
    Both Velocity and KE are listed for ammo in Midway USA's ammo section.

  12. #12
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    Quote Originally Posted by MLB View Post
    Hello Cryotech. The muzzle energy is the product of the velocity (at the muzzle) and the bullet mass.
    Not to get too technical here, but long ago Sir Isaac Newton established "how the apple falls".

    Momentum MV = Mass M x Velocity V.
    Kinetic Energy KE = Mass M x (Velocity V) x (Velocity V). That is, V squared.

    When fooling with this stuff for ammo, Mass M is in grains. Velocity V is in feet/second.
    Getting KE in foot-pounds requires figuring out a nasty conversion factor.
    I will leave THAT to the student.

  13. #13
    Steve M1911A1's Avatar
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    It's always nice to hear from someone who knows what he's writing about!

    Thanks, Dan.

    (I wonder if maybe we should PM Cryotech with all of this stuff.)

  14. #14
    kg333's Avatar
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    Quote Originally Posted by Steve M1911A1 View Post
    It's always nice to hear from someone who knows what he's writing about!

    Thanks, Dan.

    (I wonder if maybe we should PM Cryotech with all of this stuff.)
    After that disgrace of a sequel, I doubt Crytek is looking for realism. Send it to these guys: Bohemia Interactive




    KG

  15. #15
    Steve M1911A1's Avatar
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    Huh?

  16. #16
    kg333's Avatar
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    Nevermind, thought you were making a crack about Crytek. Didn't notice the OP's name...'twould appear to be a rather uncreative moniker.

    KG

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    Quote Originally Posted by Steve M1911A1 View Post
    It's always nice to hear from someone who knows what he's writing about!. . .
    Thanks Steve, a warm fuzzy is ALWAYS appreciated.

    Long ago and far away I worked 31 years in automobile passenger car safety. In a lot of different areas.

    My most favorite cartoon EVER was from around 1970. It shows two guys standing in front of a room-sized computer.
    One says "the world is full of data, much of it yearning to be analyzed". It became my motto and mantra.

  18. #18
    MLB's Avatar
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    Dan, thank you for the correction on energy vs momentum. I did indeed neglect the V^2. Always happy to see a critical set of eyes on the boards.

  19. #19
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    Cyrotech I would help you out but I'm not that savvy, I hope you can find the answer here that your looking for.

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    Quote Originally Posted by MLB View Post
    Dan, thank you for the correction on energy vs momentum. I did indeed neglect the V^2. Always happy to see a critical set of eyes on the boards.
    Thanks. And thanks for reminding me about " X^2 ". Sure saves keystrokes.

    I'm old enough to no longer worry about my memory lapses. They're too frequent for that.

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