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Energy vs. "Knockdown" for lever guns and bolt guns ...

Discussion in 'Rifle Country' started by Snakum, Jan 16, 2010.

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  1. Snakum

    Snakum Member

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    While developing a spreadsheet of energy and trajectories of the most common calibers to facilitate a rifle purchase, I marveled at the energy listed for big bore calibers like the 45-70 vs. the 30-06, 270, etc. and I remembered the debates about velocity vs. "knockdown" back in the 80s and 90s. So I started wondering if there was another way to quantify the true 'killing power' of the choices when comparing cartridges. Unfortunately, mass x acceleration just doesn't rell the while story. For example, I know a 150gr 7mm mag soft point running around 2800 fps will spin a good sized hog around and take him right down. But I've also heard stories from my brother's inlaws and guide friends about 45-70 or 444 rounds running far slower and listing far less energy figures literally knocking a mule deer off its' feet.

    I realize dead is dead. But is there a way to quantify the kind of 'knockdown power' I would gain if I bought a Marlin 45-70XLR or 444XLR over my 7600 in 270?
     
  2. KevinR

    KevinR Member

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  3. doctorxring

    doctorxring Member

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    .

    After hunting with firearms and bow/arrow for years I can
    tell you for sure it's all about punching a decent hole in the right
    spot. That is killing power.

    .
     
  4. Maverick223

    Maverick223 Member

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    What you are looking for is Taylor Knock-out (TKO) Values...and the best way to calculate them is by using a free program called PointBlank. TKO and other handy calculations are found in Misc. Functions. TKO is very controversial, but I believe it is a better approximation of killing power than energy.

    :)
     
  5. W.E.G.

    W.E.G. Member

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    Small-sample anecdotal accounts with units of measurement like "knocked off its feet" don't offer much clarity to the subject.

    A bullet fired from the same gun, one that hits a rib, or a shoulder, versus one that fails to hit bone, can have dramatically different immediate effect. A .22 rimfire that hits the spine will drop a deer like a rock. All that tells us exactly nothing.

    Its about delivering ENOUGH bullet to the vitals.
    Everything else is just story-telling.
     
  6. mshootnit

    mshootnit Member

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    Boddington wrote a good article about this awhile back. Regarding knock down power and the TKO rating of certain cartridges. Anyway after trying this stuff out on elephants, he comes to the realization that the real issue is combining a bullet that is tough and heavy enough to penetrate to the vital spot, a cartridge delivering enough speed to get it in there, and above all shot placement. The knock down power was determined to be unreliable on elephant. After careful examination of the elephant skull and practice, Karamoja Bell killed over 1000 elephants with a 7X57 shooting full metal jacketed bullets into the brain. Thats how its done.
     
  7. Maverick223

    Maverick223 Member

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    Very true...with regards to large/dangerous game I believe that the "well-accepted" trinity of desirable traits are: Caliber of .40+, SD of .30+, and velocity of 2150fps+...of course this assumes good shot placement and well constructed bullets.

    :)
     
  8. Kernel

    Kernel Member

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    There's been lots of attempts to quantify "knockdown" power mathmatically. Taylor KO. Hatcher's formula. Thorniley Stopping Power. One thing for sure, kinetic energy alone is probably the very worst.

    Now days, I like the Matunas Optimal Game Weight (OGW).

    Check out, The Killing Power of Centerfire Hunting Rifles by Chuck Hawks.

    http://www.chuckhawks.com/rifle_killing_power.htm
     
  9. Snakum

    Snakum Member

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    TKO was the one I was looking for. Thanks!
     
  10. McCall911

    McCall911 Member

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    Two that I'm familiar with:
    The TKO ("Taylor Knock Out") and OGW (Optimal Game Weight)

    The TKO was thought up by African hunter and writer John "Pondoro" Taylor to try to guesstimate the amount of time that a dangerous game animal, generally a large one, was actually knocked out by the impact of a bullet. Within these strict limitations, it might have been okay, but if you try to use it for other applications, you'll find that it fails badly. It was also not intended by the author to be any attempt at quantifying killing power. The formula for this is simply the impact velocity in feet per second X the bullet weight in grains X the caliber in inches, all divided by 1000 for "readability."

    So let me give two examples of the TKO for illustration.
    One is the original loading of the .45-70: A .458 inch bullet of 405 grains going at 1200 fps. The TKO for this bullet is 1200 x 405 x .458 / 1000 or just over 222.

    The second is a proven deer round, a .270. Let's say it has a bullet weight of 130 grains and an impact velocity of 2700 fps. So 2700 x 130 x .277 / 1000, or about 97.

    Does this mean that the .45-70 is over twice as "lethal" as the .270? I don't think so.

    The OGW ("Optimal Game Weight") takes only two variables into account: The bullet weight and the impact velocity. Basically what it amounts to is the kinetic energy times the momentum. What this means in terms of real science is nothing: Just a couple of different numbers multiplied together.

    Though these formulas may have come from respected gun writers, they have been misinterpreted to the point where they have become junk science.

    Recommended reading for anyone seriously interested in the science of terminal ballistics: "Shooting Holes in Wounding Theories."


    http://www.rathcoombe.net/sci-tech/ballistics/wounding.html
     
  11. Jack2427

    Jack2427 Member

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    Bullet placement is king, penetration is queen, everything else is angels dancing on the head of a pin. *



    *This is not my work, I am repeating wisdom read elsewhere.
     
  12. usmc1371

    usmc1371 Member

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    In the last few years I have killed a black bear with a 30-06 and a 45-70, both bears were about the same size (280#) and both were heart shots at pretty close range. The first was the 06 with a factory 180 grain remy corlock at 22 yards broadside. The bullet hit tight in behind the front sholders, passed though the lower third of the heart and exited. That bear went almost fifty yards in a second or two then just fell over and rolled down the hill stone dead. The second bear was in a hole under some boulders and was shot from the front at a distance of 4 feet, the rifle was a guide gun in 45-70 loaded with bufalo bore 405 grain hardcast lead. The big slow flat faced bullet enterd under the chin, destroyed the artaries leaving the heart, and exited just above the tail through about 5" of spine. He didn't even make a sound, just slid down the hole a few feet and died.

    My point is weather you shoot a "lighter" bullet fast or a "heavy" bullet slow it don't make much dif as long as it goes in to the right place with enough KE/TKO/OGW what ever, to do enough damage to cause death in a timely manner. With the selection of good hunting bullets around today it is not hard to use one rifle for all kinds of game, with in reason, when fed bullets matched to the game at hand.

    Last year I saw my little bro neck shoot a mule deer buck with his 338-378 and it wend down, for about 3 seconds then jumped up and ran like hell. The 250 G partition passed under the spine so it knocked it down but did no "real" damage. His second shot witch landed Texas heart shot style did all sorts of damage and ended me and my dads heyena like laughter. Two weeks later I neck shot a muly doe with my 375 HnH (260 g acubond) and all but took the head clean off. The bullet struck the spine and caused an instant drop. She didn't get up. Once again both rifles here are what most folks would call over kill but it still came down to shot placement over tons of energy.

    For the record I strongly recomend against helping with any gutting of deer shot from stern to stem with a 338-378.
     
    Last edited: Jan 17, 2010
  13. MachIVshooter

    MachIVshooter Member

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    And that's all they are. Stories. No shoulder fired small arm can actually take a 250 pound deer off it's feet.

    As far as temrinal effectiveness of one cartridge Vs. the other, no, muzzle energy is certainly not the only indicator. A .45-70 does hit a target harder than a 7mm mag, despite having lower kinetic energy. This is because the large, flat meplat of the bullet createst that much more initial contact surface. On the other side, the lower velocity of the .45-70 will not create the same nasty wound channel that the 7mm will.

    There are lots of factors that dictate the wounding mechanism of a given cartrdige and bullet. Kinetic energy is a factor, but is also overrated.
     
  14. markallen

    markallen Member

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    This might be a odd way of explaining it, but try this;
    You have two cars the same size, such as Corvettes.
    These two cars are going the same speed, and hit the same object. Result would be equal damage to the obstacle they hit. Now take the same two cars, but one is going to be going twice as fast as the other car. What will the result be on the obstacle at impact?
    Now change one of the vehicles to a...lets say Semi tractor and trailer.
    Now we have one Corvette, and one semi going at the same speed, and both hit the same obstacle. Which will do the most damage?
    If you increase the speed of the Corvette, to say twice the speed of the semi rig. It would create more damage to the obstacle, then going at the previous speed. But the semi being larger, and heavier, will still penetrate deeper, and still punch a bigger hole.
    Either way you still would need to hit the desired spot on the obstacle, but the semi will do more damage if you don't quite hit it exactly.


    There you go.....end of the caliber wars :D:D:D:D:D:D:D:D
     
  15. WatongaJim

    WatongaJim Member

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    Here's a good read discussing knockdown power vs pure energy data, written by Linebaugh. It's primarily written for handgun hunting but provides a good point of view on knockdown power in general. I like the simple calculation it provides for comparing different cartridges.

    http://www.customsixguns.com/writings/common_sense_handgun_hunting.htm
     
    Last edited: Jan 17, 2010
  16. rcmodel

    rcmodel Member in memoriam

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    One thing to keep in mind concerning bullet energy is:

    It doesn't apply if the bullet passes through the animal and buries itself in the dirt or a tree on the other side. Which most any decent hunting rifle with good bullets will do.

    Most of the bullets energy was expended on dirt.

    As for high velocity energy vs the 45-70's low, slow, & heavy?
    You don't see too many folks recommending the .220 Swift or .240 Weatherby for griz self-defense in Alaska do you?

    BTW: Heres a handy dandy calculater to play with.
    http://www.handloads.com/calc/quick.asp

    rc
     
  17. McCall911

    McCall911 Member

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    OK, so it was 7000 instead of 1000.
    7000 converts the bullet weight from grains to pounds. (7000 grains per pound)

    Let's add another example to see if the "KO" formula really holds up.
    A baseball of 2.75 inches weighing 2200 grains (about 5 ounces) thrown at 147 feet per second (about 100 mph.) So 147 x 2200 / 7000 x 2.75 = K.O. 127!!!!

    Now are we really going to say that a thrown baseball is 6 times more powerful than a .44 Magnum???

    Sorry! Mr. Linebaugh's pet formula struck out!

    :D
     
    Last edited: Jan 17, 2010
  18. Maverick223

    Maverick223 Member

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    I really need to practice my pitch...then I won't need no stinkin' gun. :D

    While the formula is not realistic, and doesn't work if anything is too big, small, fast, slow, heavy or light...it seems to be fairly accurate representation for the potential of most cartridges...that said the OGW is probably a little better. Which naturally poses the question...what is the optimal game weight for the baseball.

    :)
     
  19. Kernel

    Kernel Member

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    Terminal ballistics is about what happens INSIDE a body.

    The TKO of a baseball is zero because it makes no hole in the target. It does not penetrate.

    Otherwise, a 2.75" hole would be a pretty impressive entrance wound, and I don't care how slow it's moving!

    Perhaps, if it had razor sharp teeth and was spinning at 180,000 rpm. Like a bullet.
     
    Last edited: Jan 17, 2010
  20. McCall911

    McCall911 Member

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    Aha, but it doesn't say it has to penetrate!
    OK, let's give an example which we know is going to penetrate:
    A .308 with 165 grain bullet at 2450 fps. Doing the calculation: 165 x 2450 x .308 / 7000 "KO" = 17.7

    Are we to conclude that a .44 Magnum is going to be "more lethal" than a .308?
    I don't think so.



    My calculator says 23.1 as a max.

    If I use the example of the .44 Magnum and the .270, I get:

    .44 Magnum--237 lbs (max)
    .270 Win--755 lbs (max) :eek:

    Realistic?
    I don't think so.
     
  21. Maverick223

    Maverick223 Member

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    You took too long...I calculated 23.9lbs. :cool:

    Realistic?...I don't know, but if I were a 24lb critter I wouldn't want to get hit with a 100mph fast ball. :D
     
  22. MachIVshooter

    MachIVshooter Member

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    In terms of it's ability to knock things over, yes. In terms of lethality, obviously not.
     
  23. McCall911

    McCall911 Member

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    I mean is this realistic?

    Are we seriously going to suggest 755 lbs is the "optimal game weight" of a .270 Winchester with a 130 grain bullet?

    Even if it were true, then this means that the TKO must be dead wrong because the .44 Magnum has a higher TKO, but a much lower OGW.

    No, sorry. IMO both these formulas are out to lunch, or at best misapplied.
     
  24. RedLion

    RedLion Member

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    Simple mathematical formulas aren't going to give a clear representation of what a bullet does to its target. Nothing on here takes into account whether you're shooting hollowpoints, FMJ or marshmallows. There's nothing that describes what bullets will tumble, or which ones will fragment, or which ones might be deflected by a branch or bone. The best you can do is look at what a bullet does in ballistics gel, and look at its track record.... beyond that anyone's guess is exactly that.. a guess.
     
  25. hammerklavier

    hammerklavier Member

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    A bullet is not likely to knock a deer, man, or other large "target" over simply by energy alone. There is an equal and opposite reaction, the shooter was struck by just as much force from the kick of the gun. In fact, the shooter was hit by more force because of the additional kick from the escaping gasses, and the fact the the bullet lost some energy on the way to target.

    If firing the gun didn't knock the shooter over, it's unlikely that the bullet will knock a similar sized target over by energy alone.
     
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