Computing stopping power with John Taylor’s TKO formula
TKO, or Taylor knockout formula was created by an old african elephant hunter named John Taylor in the late 1800’s.
His formula dealt with slow moving black powder lead projectiles of the late 1800’s against elephants, and dealt mainly with near miss brain shots that incapacitated them, or simply knocked them out with that near miss to the brain.
EDIT: An Elephant skull is unlike almost any north american game animal skull that we deal with, in that the bread loaf size brain is surrounded by a spongy bone mass, it was the shock imparted to this spongy mass and whether it incapacitated the elephant by having the power to transfer that shock to the elephants brain in a near miss scenario.
The formula is mass x velocity x projectile width in inches divided by 7000.
So a 3006 with a 180 grain bullet at 2700 FPS would be 21.4 roughly.
A 375 with 300 grain bullets roughly doubles that figure.
A .177 10 grain pellet @ 1000 FPS comes in at .25.
A 18 grain exact at 900 FPS would be .51.
My Condor with 25.4 grain King at 970 FPS would be .88.
Jerry’s 70 grain slugs @800 are right at 2.0, we can see why they are so popular, at 2.0 that is a no brainer.
So you can see why we have fans of the quarter bore that use them for hunting small game and tout their effectiveness as game stoppers.
The Ranger 45 shooting a 408 grain bullet at 850 is 22.3, any idea why I consider it to be an elk gun?
Taylors formula was based on slow moving black powder lead projectiles of the day, and for many has lost it’s validity in the time of hyper velocity jacketed expanding bullets and rightly so, for to try to compare any hyper velocity jacketed bullet performance with slow moving heavy big bore lead projectiles is ludacris, there just has not been a formula so far that does it accurately.
It is apples and oranges, it does not work.
But for air gunners, dealing with the same subsonnic velocity lead projectiles, I think we can see correlations in John Taylors formula.
Plug your own numbers in as see what you get. 💡
Pellet weight x velocity x area IE., .177 or .22 or .251 and divide by 7000.
Regards,
Roachcreek
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trackers are always unarmed- not even a machete or hand ax. but they are super fast at climbing trees! still, for the $10/day they are paid, those guys are unreal. consider too that they are mainly looking straight down following tracks and not looking up to see what may be in front of them. they totally risk their lives to get you your game and absolutely depend on their boss( the PH) to protect them. any professional hunter in Africa with much experience has had his and his client’s lives saved by his tracker- and vice versa. tracker looks down- PH looks up and out. client ties to look everywhere- down and out- but with limited success. nature of the business.
Now there is the man with the balls of Steele, that tracker that was first in line.WITH OUT A GUN . 🙁
as far as Capstick goes there are 2 schools of thought. the minority opinion is that he vastly overstated his accomplishments and did indeed pick up a lot of his hunting tales will serving as a bartender early in his career while working in hunting camps. most, however( including a number of professional hunters in southern Africa who knew him well) state that he did what he said he did, but embellished the tales( sounds a lot like fishing stories, eh)
as far as Taylor’s formula goes, you just have to realize that it was derived from first hand experience shooting a lot of elephants(as well as buffalo- notoriously hard to kill) and was not meant to be extrapolated beyond. do the numbers work as far as lighter projectiles go- probably. but at the end of the day, his work was done in a whole different context.
Bell is an interesting subject. he definitely killed more elephants in his life than any man who ever lived and most with the 7×57 Mauser- certainly totally inadequate for the job- ON PAPER! but he was a master shot, had balls of steel, and was not afraid to close within 5 yards on a 12,000 lb. animal that would kill you in a heartbeat- then put that long, skinny, solid 7mm round EXACTLY WHERE IT HAD TO BE FROM ANY ANGLE. as far as elephant grass hunting goes, been there, done that( but was hunting buffalo, not eles) and you CAN NOT BELIEVE HOW SCARY IT IS. visibility is 8-10 feet at best and you are after an animal that will gladly kill you if given the chance. i felt terribly undergunned with my .375, was damn glad my PH had a .458 Lott and even happier that i was third in line behind the tracker( unarmed) and the PH.
Jerry,
I stand corrected, I did not know he was hunting in that late of an era, and why can’t it be used for airgun projectiles, because it is just for medium bores?
It can I would think at least be used to show the difference in pellet weight and bore size, even if you don’t compare it to 375’s. I mean it is just a mathamatical equation is it not? It is still used to compare by many the various 30 calibers, where do you think the cut off should be on that theory Jerry?
And like all formulas it has it’s inconsistancies too, unless there is a law or copywright forbidding it, why not? Why not apply it to what ever you want? After all it is just for fun and we are not braining elephants with our BB guns.
BTW, I read recently that Bell used to climb up on a ladder held by his men, to shoot over the tall grass and get a better angle for his 7×57, and in the same article they said that Chapstick killed most of his game in a cocktail lounge, but it would seem to me he knew these hunters he wrote about personally and did have many hunts under his belt, that was the first I had heard of any of that, have you heard those stories on the continent?
Please not trying to be arugmentive, I am just curious, after all you have been there I have not. I am just a old coyote, deer and elk murder myself.
Roachcreek
just as an FYI, John(Pondoro) Taylor was not even born until Jan. 4 1904, didn’t commercially hunt elephants until after 1927( well after the demise of black powder cartridges and the general use of smokeless powder rounds) His books “African Rifles and Cartridges” and “Big Game and Big Game Rifles” ( both published in 1948) contain his charts and formulae for “knock out values” and apply SPECIFICALLY to elephants and skull penetration. he is still considered the foremost authority among African professional hunters and experienced sport hunters on just what a medium/ large bore round will do to big game- and BTW a .375 H&H magnum is considered a medium bore round. his data CAN NOT BE EXTRAPOLATED to airguns. if you have any interest in the man and his theories, i suggest you read his biography ” A Man Called Lion” BY Peter Hathaway Capstick.
Shaggy, i was just making that comparison the other day….lol. 22 mag vs 308 Corsair.
Of course though, the 308 bullets are longer by far and have better BC and Sectional Density and are heavier.
Regards,
Roahcreek
LOL I’m learning something.
Well I have the Chrono, and I used to Log, so your right the chrono is lighter than a log LOLOL.
Shaggy, that is called a ballistic pendulum, they have been a round for centuries, and are a great tool also. We used to use them in early IPSC competition,perhaps they still do, but I think they just use a Chrony and calculator now, much lighter.
Regards,
Roachcreek
I use the TKO and the Foot Pounds formula.
Get this TKO my 308 Corseair has more TKO than a 22 magnum.
Foot Ponds, My 22 Magnum has more Foot Pounds of Energy than my 308.
I was told it wold be contriversial figure.
The best way to mesure according to an old friend of mine is hang a log on a chain and see how far eatch gun moves the log LOLOL.
You can bet the 4570 will take the prize.
Yes it is certainly not perfect by any stretch of the imagination, but at the same time gives an idea of different facets of shocking power on game.
One of my favorite deer calibers is a 22-250 Ackley improved shooting a 55 grain ballistic tip at 4000+, only comes to 7, but is akin to electrocution once in the chest cavity of a mule deer. My favorite elk medicine is a 180 Nosler partition at 3000FPS out of any 300caliber mag, it only rates 1 point above my airgun, so there are a lot of errors, but again hyper velocity was half a century in the future when Taylor calulated his foumula.
Fact is there is no perfect formula, FPE, Taylor or Smiths will all have flaws. But they are fun to tinker with. And I think come close when your looking at the difference between 17,22 and 25 caliber air rifles.
I know I certainly notice a difference on squirrels, and then get shot completely out of the park when someone slips in a Predator.
It is all just interesting history.
Regards,
Roachcreek
For bigbore airgunning purposes, I prefer Veral Smiths’ Displacement Velocity formula which is designed for use with flat nosed cast lead slugs. The only factor left for the user to figure, is how heavy of a slug is necessary for the job at hand.
The Permanent Wound Channel calculator on the Beartooth Ballisticians’ Corner page is the DV Formula.
Do you mean weight x velocity x width instead of area?
I don’t know that I really want to try it on an elephant but the number comes in at 38.1 for my .62.
Nice, My .308 Corsair pushing 128.5 gr HP’s at 900 FPS has a TKO of 5
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Looks like a rough formula for converting ball velocity into pressure (psi).
Weight (grains) X Velocity (fps) X Bullet Diameter (inches)
7000 grains (1 lb)
You would need to convert the diameter in inches to feet to pounds/square foot per second which could then be easily converted into pounds/square inch per second…
The thing that bothers me is the per second mixed into the psi number.
Is this the purpose of the formula? It would make sense if the idea was figuring penetration through hard objects of a known density…
Similar to figuring out how hard to stamp a 1″ diameter hole in a 1″ thick piece of mild plate steel with a punching press…. 😉