Rifle bullet comparisons - formula...

A

Al Thompson

Staff Alumnus
Bill Norton is the guy that I lifted this from and it seems to make sense as for relative "smack". Essentially, you use the IPSC power factor on rifles. I've played with this a bit and it seems to work. Don't have exact figures (working from memory) but here's how it looks.

Oops - forumula - bullet weight in grains times velocity divided by 1000.

.458 WM - 500 gr bullet x 2000 fps = 1000.

.416 Rem Mag - 400 x 2400 = 960

.375 H&H - 300 x 2500 = 750

.300 Weatherby - 180 x 3100 = 558

.30-06 - 180 x 2700 = 486

.270 - 130 x 3100 = 403

.223 - 55 x 3200 = 176

One has to assume like bullets, but interesting breakdown, huh? I'll post some more when I get my hands on some ballistic tables.

Giz



[This message has been edited by Gizmo99 (edited June 08, 2000).]
 
.45-70 - 400 x 1500 = 600

(mutter, grumble, "OK, I'll add another couple grains of 4895, dammit, that'll show 'em!")
 
I'll omit formulas and the various constants, okay? Sorta generalize.

The usual deal is to worry about Kinetic Energy, which is mass times velocity-squared. In reading about this through the years, it seems to me it is most useful when talking about high-speed, mucho-expansion bullets. Great big wound cavities and channels.

KE is not useful in comparing a .220 Swift to a .45-70. The latter is a .22 or .30 which has already expanded, as a certain fella has said. Big, relatively slow bullets kill by breaking bones and making a wound channel which is more dependent on the original size of that bullet. And a half-inch hole is more than I want added to me!

So, weight times velocity is more "momentum" and helps compare freight trains instead of jet planes.

So long as you're comparing apples with apples, either system works. There is absolutely no system which realistically says "this is better" when comparing varmint cartridges with elephant cartridges. That's why you'll see me so often asking, "Whatcha gonna do with it?" when newbies post questions here.

FWIW, Art
 
Why not use the Taylor Knockout Blow?

TKB=(Bullet weight x bullet diameter x MV) : 7,000

Thus,

45-70 = 400 x .458 x 1500 / 7000 = 39 :(

416 Rigby = 410 x .416 x 2400 / 7000 = 58.4 :D
 
Using that formula a 150 grain .308 at 2900 fps comes to 19.14. Is that saying that the 45-70 bullet will do twice the damage as a .308? So being shot twice with a .308 would to the same amount of damage as one shot with a 45-70?
 
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