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Thread: Thoughts About Penetration

  1. #1
    Moderator rsterne's Avatar
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    Thoughts About Penetration

    Well, this cost me a whole day playing with my spreadsheet.... *LOL*.... I spent some time with ChairGun and figured out how the math works for their Penetration calculator.... I then worked out the velocity required to penetrate various distances with a bunch of pellet weights in different calibers.... and graphed the results.... The only factors taken into account by ChairGun are the Velocity and the Sectional Density.... They don't take into account the shape or construction of the bullet.... but if you use the data for comparison purposes (eg. assume a round nosed pellet).... it should provide a decent way to compare calibers.... In simple terms, for a given velocity, a .22 cal takes a 50% heavier pellet to get equal penetration, and a .25 cal takes twice as heavy a pellet, when compared to a .177.... Here are the results.... USE THE VELOCITY ON IMPACT....



    The "non-PAL" graph shows the penetration at 450 fps, which I used for the velocity at 20 yards.... It uses an 8 gr. pellet in .177, a 12 gr. in .22, a 17 gr. in .25, and roundballs (44 gr. & 68 gr.) in .30 and .35 cal respectively.... I chose those weights because they are (except in .177) the lightest lead "pellet" available, which should mean the gun would be legal if tested.... Note that the three common calibers all have nearly identical penetration at about 1.75".... I didn't expect that, but there it is....



    I haven't assigned likely animal/bird candidates to the various Penetration numbers, as that is so much personal choice.... However, you could do things like say 1.5" is good for mice and sparrows, 3" for crows and rabbits, 5" for Marmots and Racoons, and 8" for Coyotes.... It really is up to the shooter, but I think the relationships between calibers are much easier to understand by using these charts.... For example, to have equal penetration at the same velocity, a .25 cal will require twice the FPE of a .177....



    The last set of graphs use the same method, but on big-bores.... I think from what I have read about deer hunting with air rifles, they are actually pretty darn close to what people feel is sufficient for the job.... I would use the 16" chart for deer, and possibly the 12" one for hogs.... but again, that's a very subjective thing.... Moltogordo might want to look at the last chart (24") and give it some thought as he's considering going after a bear with an air rifle....

    I'm sure I'll catch some flack over this.... but I don't really care.... I'm just trying to give people another tool to consider when they are wondering what makes sense for different size animals.... and how different calibers compare in terms of penetration.... Your comments are welcome, of course....

    Bob
    Last edited by rsterne; Jun 26 2012 at 10:32 AM.
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  2. #2
    Senior Member SeanMP's Avatar
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    Flack????Heck no. I think these charts are great comparatives and our host should probably make these a sticky or blog them.

    Of course that says nothing about my uncontrollable need to rib the h$ll outta people. What exactly did a guy do before he retired that would reverse engineer the math out of a program to make spreadsheets?

    Data Analyst for Dow Jones?

    Applied math professor at MIT?

    I mean seriously. I'm an engineer and math is a tool that will get you there but who the heck reverse engineers it for FUN?? (Admit it you were having fun)

    On a more serious note this is a great conversation starter for appropriate ammo choices. Far too often I see people raving about using ammo that offers increased penetration to hunt animals that are only 1/2 of an inch thick. Apparently Mrs Roosevelt was right.
    Sean

  3. #3
    Moderator rsterne's Avatar
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    It actually wan't too hard to do, and yes, it fulfilled my definition of "fun" at the moment.... Once I realized the only variables were velocity and SD (and that they were both linear variables), it was just a matter of figuring out the constant they were using.... I've read several places that those are, indeed, the only factors governing penetration, assuming a constant nose shape, no distortion, and no tumbling.... all of which happen in the real world.... Pellet choice is still a matter of delivering the most energy on target downrange, and then having the target absorb it as completely as possible once penetration to the vitals has been achieved.... None of those things are easy, and they tend to be mutually exclusive to a degree.... However, they apply to all calibers equally, so the basic math still give a valid comparison....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

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    Administrator AirGunEric's Avatar
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    I wanted to post some thoughts about penetration- then realized this wasn't the porn site I meant to click on...


    I'd say I care- but I'd probably be lying...


  5. #5
    Moderator rsterne's Avatar
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    T.M.I..... waaayyyyyyyyyyyyyyyyyy T.M.I....................................

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  6. #6
    Senior Member sholo's Avatar
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    Quote Originally Posted by AirGunEric View Post
    I wanted to post some thoughts about penetration- then realized this wasn't the porn site I meant to click on...


    ...LMAO!!!...

    I might have to re-think this "local pick up"...afraid of what I may walk in on!

    Todd
    Todd

    Don't sweat the petty things, and don't pet the sweatty things!

  7. #7
    Senior Member Doc Sharptail's Avatar
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    Ahh yes, the "real world". Amazing are the variables that it will throw at you.

    I'd really like to see some more on those cross cut dum-dums that (coff-hint coff-hint) Bob had mentioned a while back.

    From what I've been seeing from my arsenal of mediocre power- on living tissue- has been 100% over penetration. Traces of expansion on living tissue are so slight it ends up being a negligible point.

    I still suspect that I'm not driving the predators fast enough for them to expand properly. On semi-soft test media, the .22 cal. JSB exact heavies show a lot of promise. I really need to connect with these on live game.

    Regards,

    Doc Sharptail
    "Ain't No Half Way"

    -S.R.V.

  8. #8
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    I make some pellets, that have terrific penetration, I'll take an H&N Crow Magnum and add a tiny drop of super glue, and place a Daisy BB on top, when the glues dry they're inseparable.They come out to around 23gr, and are extremely accurate, the smaller bb is centered in the crow magnum so it doesn't touch the ******s rifling. Impact, is terrific with the bb being pushed straight down, and the sides folding down, On the occasion when I do see them flying through the scope the trajectory is extremely flat, and they fly pretty fast too, a while back I used them paired with a modded QB 78D, and made an incredible 50 yd shot that put a Jack Rabbit on the table that night,,I always keep a good supply on hand, and it only takes a few minutes to make a hundred or so. Cheer's, Andy.

  9. #9
    Hi Andy, ... and thus proving that desperation is the father of invention. An idea after my own heart... superglue as a tool to increase pellet weight. You machinists can chuck that in your lathe and spin it Huh? he he he

    Seriously, Bob I am impressed. I really appreciate you guys doing all the heavy lifting. Of course I have a question for you Bob.... What distance would these theoretical penetrations take place? You mention 20 yards in the nonPAL. Is it the same for each charts? Or, do we assume muzzle velolcity and then crunch the drag numbers to get fps at distance of the intended impact?

    Theoretically the Youtube "dealer" advice that you cannot take any type of small game with .177 would be a marketing driven conclusion.???? From your charts I might assume that maybe even a detuned target pistol in .177 could possibly be adequate for pest extermination... based on muzzle velocity, close range, and mathematical constructs.

    Thanks guys,

  10. #10
    Moderator poil27's Avatar
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    been model making for the most part of 20 yeas ant i've learn to apreciate cyano acrylate (super glue) in an whole new fation when one of my folow modeler showed me how to make a super light ans solid composite material with it. just add baking soda it will sliidified instantly and fill up gap .

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