I'm putting this here because this is more of a ballistics question, but has a hunting bent.

First, I understand that all the math in the world is to ballistics as benchracing is to the drag strip, but I feel it has some merit for gaining general starting points and such. So lets not get carried away.

I believe that many have a general acceptance of the Taylor Knock Out (TKO)rating for hunting performance, if only limited.

If I understand correctly, the rating is derived by:

[(velocity) * (bullet weight) * (caliber)] / 7000

Taking 25ACP load data from a book, the TKO for a 50gr .25 cal bullet at 700fps would yeild a TKO of:

[700 * 50 * 0.25] / 7000 = 1.25

Doing the same for 38spl, with a 140gr @ 500fps, yields:

[500 * 140 * 0.357] / 7000 = 3.57

So in general, one would assume the light 38spl loading would be superior to the hot 25ACP loading, for game. Makes sense and does not contradict common sense, bullet construction aside.

Now, I have a kick-ass slingshot that I generally use for paintballs. But I've been testing some ballistics with it (see "Getting the Most from your Chrony" available at Bookstores soon )

I can carry a 15gr .25cal steel BB to 250fps. I can take a 250gr lead bullet to 180fps. This means TKOs of 0.13 and 2.89 respectively (assuming the minimum diameter for a hit with the lead bullet).

Now, judging from the way grackles just laugh at you when you body-shoot them with the BBs, and judging from the effect of these two types of ammo on wooden fences, plastic buckets, beer cans and bricks, it is obvious that the bullet would be much better on game than the BB.

But carrying it a step farther, would the slingshot do better than the 25ACP on game? Forgetting again bullet construction, trajectory and range of course.

What are the general limitations of the TKO rating? Where does it fall apart? Or is this reasonable? Sounds freaky to me, but then again, I have yet to hit any game with the big ol bullet.

The taylor formula is to compare centrefire nitro cartridges.
It falls apart as soon as you put shotgun slugs, bore guns, rocks, frisbies or lead sinkers into it.

Karl.

[This message has been edited by Karl (edited 02-10-2002).]

TKO ratings were based on the use of solids on elephants and it is a very accurate measure, in that experience in shooting elephants and Buffalo and its relationship to killing power is quite the same as Taylor said it was....I have no clue about bbs' and slingshots, that's just more than I can handle at the moment. Let me know how it turns out for you.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

I second Ray's remarks. Taylor himself said that his TKO formula had nothing whatsoever to do with killing power for any bullet striking the vitals in the thorax of a game animal. That it has been extrapolated to such use is not his fault.

Your BB "load" has 2 ft-lbs of kinetic energy. The lead bullet "load" has 18 ft-lbs. It "absorbs" more of the available energy of the slingshot and probably arrives with more remaining. It probably doesn't penetrate as well against skin, being larger and somewhat slower but the blunt trauma would be more severe with 9 times the KE. Why not shoot both of them into a block of modeling clay and report to us the "wound" channel created?

Oooh! Yes! Play-Do ballistics tests!

Its not like I'm going after coyotes or whatever. Just playing around. Maybe I can also see how easiliy it knocks a playdo block over?

As for its usefulness, I did not know that about the TKO. I had seen taffin use it to claim a 45LC would equal a 44mag in some applications. I assumed it was okay to universally apply it, within set windows of application.

Surprise,
The hot loaded 45 Colt is as effective a killer as the 44 Magnum..the better cross section means a great deal in big slow bullets...

A cast 45 Colt is an awsome killer of big game at close range...I prefer it to the 44 Magnum, but there isn't a lot of difference..My good friend Ross Seyfried, who has shot a lot of big game with both prefers the 45 Colt..

My experience is very limited to about 2 deer with the Colt and 3 with the 44 Mag, and one with a 41 Mag, not a lot of difference in any of them that I could see, other than I got a better blood trails with the Colt, but 2 deer proves little.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

Ray, I'm not doubting that at all.

I was curious if the same principles of using TKO could be generally applied to most any projectile or if it has limitations. My example was in the extreme, I'm not ready to go hog hunting with a slingshot

I believe that the key to a proper answer to your question lies approximately in the field of medicine. Animals die or stop shooting at you or whatever because of wounds. Like, penetrating enough to cut large blood vessels, if the FMC doesn't push the blood vessel aside, or severing a spinal cord, or turning a brain to mush. You CANNOT usually ignore bullet construction. Penetration counts, which probably relates to sectional density first, velocity second, and bullet construction. Taylor's TKO, as pointed out above, was intended to compare a very limited number of variables over a fairly small range with others eliminated, applied to a particular shot placement. He wisely defined the limits of his comparison.

There are probably no simple mathematical relationships, or maybe none at all, that describe "killing power" or "stopping power" over an unreasonably wide range of input values. When you have simple relationships, you have formulas that show a tennis ball having SOME stopping power. But it doesn't, at least not at real-life velocities. Not a little, not VERY little, but none at all. Yet that's not what your calculation shows.

So much for simple answers.