MaraviaDave
WKR
From my perspective, this article BULLET “ENERGY” (ft-lbs) VERSUS “TKO” EFFECTIVENESS ON BIG GAME (buffalobore.com) makes a good case that the measurement used for bullet energy (Kinetic Energy) by most hunters may not be the best for quantifying terminal ballistic effectiveness on larger sized big game animals.
A couple of key points from the article in regards to KE are as follows;
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 bullet diameter, which is very important as the quarry gets bigger and tougher.
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.
Here's an example from the article that illustrates the point;
"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. bullet moving @ 3,850 fps generates a slightly higher number of 1,645 ft-lbs, but let me ask, which load would you want to hunt grizzly with?…..or better, which load would you want to try and stop a charging grizzly with?"
The author presents the Taylor Knock Out (TKO) formula as a better alternative to KE for measuring cartridge/bullet effectiveness, on heavily constructed game animals, in comparison to less heavily constructed game animals. However, there is an application for KE, which he explains;
So, where/when are kinetic energy numbers meaningful when applied to kill mammals? I believe that with super thin skinned, lightly constructed animals that weigh under 200 lbs., kinetic energy has a meaningful application, but remember that those kinetic energy numbers are still coupled with other factors that we cannot give a value to, such as bullet construction (mushrooming, fragmentation, secondary projectiles such as bone fragments, state of mind of the mammal being shot, etc., etc., etc.) and depth of penetration, etc. Thin-skinned smaller animals like whitetail deer, humans, coyotes, etc. are all susceptible to the effect of faster lighter bullets. These types of animals do not require super deep penetration to be killed, so kinetic energy numbers have meaningful application, but not so with buffalo, grizzly, moose, etc. From a great deal of personal experience, I can tell you that the above 22-250 load would literally explode a 4 lb. Rock Chuck hit within normal shooting distances, but the old 45-70 load would just make a big hole in a Rock Chuck……..so the Kinetic energy calculation is more meaningful with the small mammals, than with giant mammals.
***please read the original article, by clicking the link above, for full context***
Recognizing that there are other energy calculations out there, each one having supporters and detractors, I built spreadsheets to compare the rifle/bullet combinations I hunt with, using the various formulas. Doing this has helped me become aware of the the biases (e.g. velocity, bullet weight sectional density, cross-sectional area, etc), considered for each formula.
Of course there are things not accounted for in the formulas. Specifically bullet construction (frangible vs controlled expansion) and shot placement. Shooting a moose quartering towards you, requires more from a bullet / impact energy / terminal ballistic perspective, than center punching the lungs of a broadside bull.
In addition to helping make more informed decisions about cartridge selection for different hunting applications. I also believe the value of these formulas are to assist in making comparisons between bullet options in a given cartridge type.....in regards to choices of bullet weight and efficiency (BC) and the subsequent impact velocities at distance.
If you'd like to make your own comparisons, use the formulas listed below;
Kinetic Energy (ft-lbs)
(velocity)^2*(bullet weight) / 450440
Optimum Game Weight (lbs)
(velocity)^3*(bullet weight)*1.5*10^-12
Taylor K.O. Factor
(bullet weight)*(velocity)*(bullet sectional density) / 7000
**Bullet SD= ((bullet weight)/7000)) / ((bullet diameter)^2)
Momentum *ft-lbs)
(bullet weight)*(velocity) / 6990.78
Killing Power Score
(kinetic energy)*(bullet sectional density)*(bullet cross sectional area)
**Bullet SD= ((bullet weight)/7000)) / ((bullet diameter)^2)
**Bullet CSA= ((bullet diameter) / 2)^2*3.1416
A couple of key points from the article in regards to KE are as follows;
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 bullet diameter, which is very important as the quarry gets bigger and tougher.
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.
Here's an example from the article that illustrates the point;
"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. bullet moving @ 3,850 fps generates a slightly higher number of 1,645 ft-lbs, but let me ask, which load would you want to hunt grizzly with?…..or better, which load would you want to try and stop a charging grizzly with?"
The author presents the Taylor Knock Out (TKO) formula as a better alternative to KE for measuring cartridge/bullet effectiveness, on heavily constructed game animals, in comparison to less heavily constructed game animals. However, there is an application for KE, which he explains;
So, where/when are kinetic energy numbers meaningful when applied to kill mammals? I believe that with super thin skinned, lightly constructed animals that weigh under 200 lbs., kinetic energy has a meaningful application, but remember that those kinetic energy numbers are still coupled with other factors that we cannot give a value to, such as bullet construction (mushrooming, fragmentation, secondary projectiles such as bone fragments, state of mind of the mammal being shot, etc., etc., etc.) and depth of penetration, etc. Thin-skinned smaller animals like whitetail deer, humans, coyotes, etc. are all susceptible to the effect of faster lighter bullets. These types of animals do not require super deep penetration to be killed, so kinetic energy numbers have meaningful application, but not so with buffalo, grizzly, moose, etc. From a great deal of personal experience, I can tell you that the above 22-250 load would literally explode a 4 lb. Rock Chuck hit within normal shooting distances, but the old 45-70 load would just make a big hole in a Rock Chuck……..so the Kinetic energy calculation is more meaningful with the small mammals, than with giant mammals.
***please read the original article, by clicking the link above, for full context***
Recognizing that there are other energy calculations out there, each one having supporters and detractors, I built spreadsheets to compare the rifle/bullet combinations I hunt with, using the various formulas. Doing this has helped me become aware of the the biases (e.g. velocity, bullet weight sectional density, cross-sectional area, etc), considered for each formula.
Of course there are things not accounted for in the formulas. Specifically bullet construction (frangible vs controlled expansion) and shot placement. Shooting a moose quartering towards you, requires more from a bullet / impact energy / terminal ballistic perspective, than center punching the lungs of a broadside bull.
In addition to helping make more informed decisions about cartridge selection for different hunting applications. I also believe the value of these formulas are to assist in making comparisons between bullet options in a given cartridge type.....in regards to choices of bullet weight and efficiency (BC) and the subsequent impact velocities at distance.
If you'd like to make your own comparisons, use the formulas listed below;
Kinetic Energy (ft-lbs)
(velocity)^2*(bullet weight) / 450440
Optimum Game Weight (lbs)
(velocity)^3*(bullet weight)*1.5*10^-12
Taylor K.O. Factor
(bullet weight)*(velocity)*(bullet sectional density) / 7000
**Bullet SD= ((bullet weight)/7000)) / ((bullet diameter)^2)
Momentum *ft-lbs)
(bullet weight)*(velocity) / 6990.78
Killing Power Score
(kinetic energy)*(bullet sectional density)*(bullet cross sectional area)
**Bullet SD= ((bullet weight)/7000)) / ((bullet diameter)^2)
**Bullet CSA= ((bullet diameter) / 2)^2*3.1416
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