On 2008-03-31, Gig 601Xl Builder wrote:
I know you think IPSC shooting is a game and has little to do with the
real world but it's power factor system is as good as any of calculating
the force projected on target.

9mm = 135 gr @ 1100 fps = 135,300
.40 S&W = 165 gr @ 980 fps = 161,700
.45acp = 230 gr @ 900 fps = 207,000

Hmm, that is just 'gr' x 'fps' (except for the 9mm which seems wrong).

This analysis is flawed. Kinetic energy isn't just mass x velocity.
K = 0.5 mv ^ 2

(where K is the kinetic energy, m is mass in kilograms, and v is velocity in
m/s).

So converting to SI so we can calculate the kinetic energy:
9mm = 8.75 grams at 335 m/s
..40 = 10.7 grams at 299 m/s
..45 = 15 grams at 274 m/s

Which results in:
9mm = 491 joules
..40 = 478 joules
..45 = 563 joules

So while the .45 has the most kinetic energy, the 9mm actually beats the
..40 when the calculations are done according to the laws of physics.

So I'd argue its power factor isn't any good at all since it's based on
a fundamentally flawed calculation. I won't disagree that there may be
other factors when considering the effectiveness of a round, but just
multiplying mass by velocity is so wrong it's not even wrong.

--
From the sunny Isle of Man.
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