The Energy to Pressure of Combat Pistol Cartridges


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About the Chart

Lyman Reloading Handbook 49th Edition:
Energy (Ft./Lbs.) = (Bullet Weight * Velocity^2) / 450400
Where bullet weight is in grains and velocity is in feet per second.
Most velocities come from BuffaloBore's website, a good authority.
SAMMI pressures are used, when a SAMMI pressure for a round is unavailable, a percentage of increase by (observing neighboring cartridges) estimate is used.
Everything with a velocity of 1126 and above is highlighted to denote supersonic (1125 FPS is the speed of sound at standard temperature at sea level)
Pressures are sited from SAAMI.ORG
Velocities and Weights (Energy) sited from

What I learned

The non-straight-walled cartridges are visibly less efficient.
The exterior .45ACP geometry produces the highest power to pressure out of any production combat auto-loading pistol cartridge in the world, including that of the U.S. military.
9mm at standard pressure maintains the same energy as .380+p
200gr .45 SUPER possesses the same energy as 200gr 10MM with less pressure.
9mm must be powered down to be subsonic with the heaviest bullet. (As listed from BuffaloBore)
10MM Really IS an auto-loading .357 Magnum!
I like .40 Smith and Wesson a little more now.


.50GI and .50AE are listed, Range, and capacity and size have most likely precluded these rounds from becoming mainstream combat rounds. But man, just look at those stats.
Usual USPSA power factor is 165.
Power factor = Bullet Weight * Velocity / 1000
Where bullet weight is in grains and velocity is in feet per second.
Cartridges with the versatility of loads that produce the same energy with both sub-sonic (heavy) and super sonic (light) projectiles can be useful for suppressor systems.
Energy to Pressure was calculated by: Energy (Ft./Lbs.) / Pressure (PSI) * 1000
(The Higher the ETP the more efficient the cartridge)

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