Energy relates to how much stored up work can be done and is based upon the mass of the projectile divided by two and its velocity squared. Momentum relates to the duration and force required to start or to stop an object and is based upon mass and simple velocity. Ammunition manufacturers use energy to describe the power of a cartridge. US Army field studies slaughtering cattle indicate that power may be more closely related to momentum. The answer may lie somewhere in the middle. The concept of stopping power adds more complexity, because target anatomy and shot placement may be more important than anything else. Firepower can be demonstrated by a .50 cal machine gun burst, but unless the target is hit, a well placed .22 would have more stopping power. In a gunfight, the successful outcome depends most upon the mindset developed by positive attitude and preparation, and skill from practicing with reliable equipment.
**This table of stopping power uses a formula favoring momentum over energy.
The formula multiplies the bullet’s base area in square inches times its weight in grains times its velocity in feet per second, then divides by an arbitrary number (1000) to get a result which can be compared easily.
*
Caliber Bore Diameter Base Weight Velocity Power
*
454 Casull .451 .1598 300 1630 78.14
44 Magnum .429 .1445 240 1400 48.55
41 Magnum .410 .1320 250 1250 41.25
*
45 ACP .451 .1598 230 850 31.24
40 Smith & Wesson .401 .1263 180 990 22.51
357 Magnum .357 .1001 158 1240 19.61
*
9mm Luger .355 .0990 124 1120 13.75
38 Special .357 .1001 158 760 12.02
380 Auto .355 .0990 95 1000 9.41
*
32 Auto .308 .0745 65 950 4.60
25 Auto .250 .0491 50 800 1.96
22 Long Rifle .220 .0380 40 900 1.37
see
http://www.gunthorp.com/wounding_factors.htm
I personally stick with heavier bullets for each caliber, and practice with the equivalent weight and power of the loads I carry. But, hey, try different weights anyway. Heavier bullets offer more penetration and recoil. Be sure of your background when a skinny gangbanger tries to threaten you, but you'll appreciate the heavy bullets if you run into a 300# meth freak.