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NEW BUFFALO BORE APPAREL
BULLET “ENERGY” (ft-lbs) VERSUS “TKO” EFFECTIVENESS ON BIG GAME
Friends, please understand that this is a very complex subject, with many known and unknown variables that cannot be addressed or defined completely in an essay. Even if we wrote a book on this subject, we could not cover it completely. Please do not find fault with the fact that this essay could be 500+ pages long, but isn’t. This essay is an attempt to bring awareness to our customers, not to be 100% conclusive on the subject.
Many decades ago, some gun writers started comparing cartridge effectiveness by measuring and applying the cartridges ft-lbs (Kinetic) of energy. That trend of using ft-lbs to calculate “killing power” has become pervasive, industry-wide. Kinetic energy may be a useful tool for measuring some things, which we will discuss, but today, ft-lbs of energy calculations are being applied in ways that are very misleading or not accurately applicable.
First, let’s take a look at the mathematical calculation for bullet kinetic energy or ft-lbs of energy.
Let’s look at kinetic energy calculations for a typical 30-06 load of a 180gr.
So what’s the problem????
The “problems” are several and meaningful!
1. First, this formula uses velocity squared, so it will always give higher values to lighter, faster bullets and lighter, faster bullets are meaningless to an 800 lb. bull elk or more especially to a 2,000 lb. stomping mad Cape buffalo.
2. Second, this calculation ignores
3. Third, this calculation ignores bullet shape..i.e. in general terms; a round nosed solid/non-expanding bullet will do less terminal damage than a flat nosed solid bullet.
4. Fourth, it ignores bullet construction.
As one example of the flawed ft-lbs formula, let’s look at one very early and popular good old standby 45-70 load compared to a modern 22-250 load.
The early 45-70 gained much of its big game killing fame by pushing a 405gr. lead round nosed bullet @ 1,350 fps with black powder….this load generates 1,638 ft-lbs of energy……The typical 22-250 load of a 50gr.
Let’s come back to the discussion of the usefulness of kinetic energy numbers after we discuss the TKO mathematic formula.
TKO - Taylor Knock Out
TKO stands for Taylor Knock Out. John Taylor was a mid-20th-century African hunter and poacher. Nobody knows how many thousands head of African game he killed, but it was several. His original KO formula was derived by observing how effective certain cartridges were in knocking out an elephant if it was shot in the head, but the brain was missed.
Taylor’s mathematical formula is thus. Bullet diameter X weight in grains X velocity / 7,000 (7,000 grs. in one lb.)
Bullet Diameter X Bullet Weight X Velocity
7,000 (7,000 grains = 1 lb)
Taylor's KO formula still does not factor the bullet shape, but assumes solid, non-expanding construction and does include the very important bullet diameter and further, it does not square the velocity but gives velocity the single value it deserves. TKO numbers only have relevance if they are being compared to other TKO numbers…..comparing TKO numbers to ft-lbs would have no meaning.
The same above 30-06 load that we calculated would have 2,913 ft-lbs of energy for would give a TKO # of 21.39
Let’s compare the same 45-70 and 22-250 loads that we used in the above ft-lbs comparison……
See what happens when you include bullet diameter and do not square velocity? The old weak black powder 45-70 load generates a rating of 5X what the 22-250 load generates, for effectiveness on big game.
Is the TKO rating perfect for generating a number that will predict effectiveness on big game? No, absolutely not! No mathematic formula could be. However, the TKO formula will generate a number that I believe is far more meaningful on big game, than ft-lbs of energy.
BIG GAME (TKO) vs SMALL GAME (ft-lbs)
So, where/when are kinetic energy numbers meaningful when applied to kill mammals? I believe that with super
This would be a good place to refer you to a
Often, we over-think a topic and never come to a useful resolution, so let’s find the lowest common denominator in this discussion…..for
Choose your cartridge and your ammunition for that cartridge accordingly. Obviously, it will require some kinetic energy to get that bullet downfield and to penetrate the target sufficiently, but bullet size and design is a bigger part of that formula than kinetic energy
Hopefully, this essay will be useful to those of you who have been drinking the industry cool aid about kinetic energy that is
Good shooting and God bless,