The Thorniley Stopping Power Formula is similar to the Taylor KO Factor we studied in the previous page. It is calculated as:
TSP = 2.866 * v * (m/7000) * sqrt(d)where:
TSP = Thorniley Stopping Power
v = velocity of the bullet in feet per second
m = mass of the bullet in grains
sqrt = square-root function
d = diameter of the bullet in inches.
Since this formula uses the square-root of the bullet's diameter (unlike the Taylor KO factor formula, which uses the bullet's diameter without taking the square root), the values are on a different scale than the Taylor KO factor numbers. Like the Taylor KO factor, the values obtained by the TSP formula are empirical.
The Thorniley scale is as follows:
|Thorniley Stopping Power||Suitable For|
|50||White-tail Deer, Mule Deer etc.|
|120||Elk, Moose, Kudu, Zebra etc.|
|150||Lion, Leopard, Grizzly Bear, Brown Bear|
|250||Hippopotamus, Rhinoceros, Cape Buffalo, Elephant|
Let's say that we have a .30-06 rifle (such as the M1903 Springfield rifle or the M1 Garand rifle). Let us assume that this rifle fires a bullet weighing about 180 grains and .308 inch diameter moving at around 2900 feet/sec. Plugging the numbers into the formula above, we have:
TSP = 2.866 * 2900 * (180/7000) * sqrt(0.308) = 118.61 approximately.
Looking up the TSP value on the table above, we see that a .30-06 rifle can be used to hunt antelopes, deer, black bears, elk, moose, kudus, zebras etc. (since 118.61 is pretty close to 120), but probably not such a good idea against lions, grizzly bears, hippopotamuses, rhinoceroses, elephants etc.