The Taylor Knock Out (TKO) was an index meant for solid bullets used on elephant skulls for a Knock Out with a near-brain miss. The TKO was OK, or not, depending on whose opinion was rendered. It was basically a product of caliber, weight and velocity of the bullet, with some constants thrown in for unitary consistency.
I propose a simplified new index for application to soft point bullets used on big game. Coincidentally the numeric value of this new Lethality Index equals the weight of the game animal, in pounds, for which it is adequate. It will be called the Game Weight Index (GWI) of the load. It is very simple, but requires impact range adjustment of velocity, like Sir Bob's MTE.
GWI = (fps bullet velocity at impact )x(grains bullet weight) / (inch-caliber of bullet)x(1000) = Maximum game weight in pounds on the hoof, for the soft point load suitability.
Try it, you will like it.
For .375 H&H with 300-gr Barnes TSX (BC = 0.357)
2500 fps at 000 yards: GWI = 2500x300/.375x1000 = 2000# 2263 fps at 100 yards: GWI = 2263x300/.375x1000 = 1810# 2041 fps at 200 yards: GWI = 2041x300/.375x1000 = 1633# 1832 fps at 300 yards: GWI = 1832x300/.375x1000 = 1466#
Let us compare the .458 WinMag with 400-gr GSC HV (BC = 0.372) ... the upcoming 400-gr/.458-cal Shock Hammer should be very similar in BC ...
2500 fps at 000 yards: GWI = 2500x400/.458x1000 = 2183# 2273 fps at 100 yards: GWI = 2273x400/.458x1000 = 1985# 2058 fps at 200 yards: GWI = 2058x400/.458x1000 = 1797# 1856 fps at 300 yards: GWI = 1856x400/.458x1000 = 1621#
Another old favorite of mine and Sir Bob, the .340 WbyMag with 250-gr Nosler Partition (BC = 0.473) at 2818 fps (most accurate load in Nosler #9, and as modest as the above .375 & .458 loads)
2818 fps at 000 yards: GWI = 2818x250/.338x1000 = 2084# 2625 fps at 100 yards: GWI = 2625x250/.338x1000 = 1942# 2440 fps at 200 yards: GWI = 2440x250/.338x1000 = 1805# 2263 fps at 300 yards: GWI = 2263x250/.338x1000 = 1674#
A .375 H&H 300-grainer at 2500 fps is a classic sort of load that has been judged "adequate" by most. Good for an 1800-pound buffalo inside of 100 yards. The .458 WinMag with 400-grainer might be better, at all ranges to infinity. The .340 WbyMag might be barely better at 200 yards, but not at 100 yards, where buffalo should be shot.
The 450-gr TSX in the .458 WM+ with a tropical load (BC = 0.369), Sir Jerry does a bit better than this with his M70 rifle with 3.6" box and SAAMI .458 WinMag chamber:
2400 fps at 000 yards: GWI = 2400x450/.458x1000 = 2358# 2176 fps at 100 yards: GWI = 2176x450/.458x1000 = 2138# 1966 fps at 200 yards: GWI = 1966x450/.458x1000 = 1932# 1768 fps at 300 yards: GWI = 1768x450/.458x1000 = 1737#
With a proper 500-gr soft at 2350 fps in the .458 WM+, consider MV only, pending BC of the unspecified soft bullet:
2350 fps at 000 yards: GWI = 2350x500/.458x1000 = 2566#
I like this. Good as any lethality index and easily calculated. It equally weights velocity and bullet weight and by dividing by caliber favors sectional density. Impact velocity factors in the BC. What can possibly be wrong with this ?
Great, Sir Ron,
The only change I'd make would be in using the CSA of each caliber rather than the nominal caliber, for this reason: The distinction between calibers isn't linear but in area, and that is a significant factor to be considered. For instance: .375/.458 = .8188, or say the .375 is 82% of a .458, whereas in reality the distinction in cross-section-area is .110/.165 = .6666, or say the .375 is in reality only 67% of a .458. Just a further consideration, but I don't want to mess with the simplicity of your GWI.
