The Taylor Knock-Out Factor (TKOF)

By Chuck Hawks

The late John "Pondoro" Taylor (1904-1969) was an Irish remittance man, ivory hunter and poacher who hunted in Africa for some 30 years before finally being expelled for his transgressions. He became a self-styled expert on big game hunting rifles and wrote several books about African hunting and firearms. He is best known as a hunter/poacher of thick-skinned dangerous game (Class 4), particularly buffalo and elephant.

Taylor introduced his KO Factor in African Rifles and Cartridges (1948). He devised his KO Factor formula to conform to his personal experience with big bore cartridges shooting heavy bullets. His experience and opinions were based on 1930's and 1940's bullet technology. If you made your living by poaching elephants for their ivory in Taylor's time, it made sense to use a heavy caliber rifle. Today, ivory poachers machine gun elephants with AK-47 assault rifles, which (unfortunately) also seems to work.

The Taylor Knock-Out Factor (TKOF) was intended to be comparative, allowing the stopping power of one cartridge/load to be compared to another. The TKOF numerical values do not represent any scientific quantity or unit of measurement (fps, ft. lbs. etc.). In this, TKOF is like Hornady HITS or the G&S Online Rifle Cartridge Killing Power numbers, albeit with a far lower correlation to reality.

The TKOF formula multiplies bullet weight in grains by bullet velocity in fps by bullet diameter in inches and then divides the product by 7000 (the number of grains in a pound). This formula intentionally favors large diameter, heavy bullets, which are what Taylor was shooting most of the time (surprise, surprise). Pondoro provided no objective evidence to support his selection of these factors (bullet weight, diameter, velocity and the constant 7000) as particularly germane to stopping power and, as it turns out, they are not. (What about energy, sectional density, frontal area and expansion?--don't ask Pondoro.) Thus, the KO Factor often makes no sense. For example, here are the TKOF's for four well known hunting cartridges:

  • .38-55 Winchester, 255 grain at 1650 fps = 22.8
  • .35 Remington, 200 grain at 2100 fps = 21.1
  • .30-06 Springfield, 170 grain at 2850 fps = 20.8
  • .30-30 Winchester, 150 grain at 2250 fps = 14.9

I don't think it would take most big game hunters long to spot serious discrepancies in this brief list. Taylor's formula results in the .38-55 and 35 Remington being rated above the much more powerful .30-06. Note also that the .30-30 Winchester is based on a necked-down .38-55 case and historically both cartridges were used to hunt the same animals; the .30-30 proved so superior to the .38-55 that the parent cartridge quickly became obsolescent. Clearly, there are serious problems with the TKOF formula.

This is a perfect example of what happens when a stopping power formula is devised to affirm one's personal prejudices. Taylor claimed that his KO Factor closely matched his personal experience and I believe him. The problem is that Taylor was a fan of big bore elephant cartridges shooting solid (non-expanding) bullets. Unfortunately, in many cases TKOF bears no resemblance to reality when applied to more common Class 2 (deer size game) and Class 3 (elk size game) hunting cartridges shooting expanding bullets. The Taylor Knock-Out Factor is antiquated, inaccurate and should not be used as a reference in stopping power discussions, although some writers still persist in doing so.

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Copyright 2013 by Chuck Hawks. All rights reserved.