Ballistics are a slightly tricky lot. This is due to the firearms themselves.
A 2" snubbie .357, vs. a 6 or 8" barrel length. etc,....
Here's the skinny:
http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNBLST.htmlThe term ballistics refers to the science of the travel of a projectile in flight. The flight path of a bullet includes: travel down the barrel, path through the air, and path through a target. The wounding potential of projectiles is a complex matter. (Fackler, 1996)
Internal, or initial ballistics (within the gun)
Bullets fired from a rifle will have more energy than similar bullets fired from a handgun. More powder can also be used in rifle cartridges because the bullet chambers can be designed to withstand greater pressures (70,000 psi vs. 40,000 psi for handgun chamber). It is difficult in practice to measure the forces within a gun barrel, but the one easily measured parameter is the velocity with which the bullet exits the barrel (muzzle velocity) and this is what will be used in examples below.
The controlled expansion of burning gunpowder generates pressure (force/area). The area here is the base of the bullet (equivalent to diameter of barrel) and is a constant. Therefore, the energy transmitted to the bullet (with a given mass) will depend upon mass times force times the time interval over which the force is applied.
The last of these factors is a function of barrel length. Bullet travel through a gun barrel is characterized by increasing acceleration as the expanding gases push on it. Up to a point, the longer the barrel, the greater the acceleration.
As the bullet traverses the barrel of the gun, some minor deformation occurs, called setback deformation. This results from minor (rarely major) imperfections or variations in rifling or tool marks. The effect upon the subsequent flight path of the bullet is usually insignificant. (Jandial et al, 2008)
Bullets produce tissue damage in three ways (Adams, 1982):
1.
Laceration and crushing - Low velocity bullets, as in handguns, that travel less than 1000 fps do virtually all their damage via crushing.
2.
Cavitation - Cavitation is significant with projectiles travelling in excess of 1000 fps. A "permanent" cavity is caused by the path of the bullet itself, whereas a "temporary" cavity is formed by continued forward acceleration of the medium (air or tissue) in the wake of the bullet, causing the wound cavity to be stretched outward.
3.
Shock waves - Shock waves compress the medium and travel ahead of the bullet, as well as to the sides, but these waves last only a few microseconds and do not cause profound destruction at low velocity. At high velocity, generated shock waves can reach up to 200 atmospheres of pressure. (DiMaio and Zumwalt, 1977) However, bone fracture from cavitation is an extremely rare event. (Fackler, 1996)
The mathematics of wound ballistics, in reference to yaw of unstable projectiles, has been described. The model works well for non-deformable bullets. (Peters et al, 1996)(Peters and Sebourn, 1996)
Or a .45 (note the barrel length used.)
http://www.handloads.com/misc/stoppingpower.asp?Caliber=18&Weight=230At the link, you can change calibers and bullet weights, all this is from Ed Sanow's book Stopping Power.
It's not gospel, but is brain food.
Here's another.
http://findarticles.com/p/articles/mi_m0BQY/is_2_47/ai_68704858/Ballistic Realities: Barrel Length & Bullet Penetration
Hey,... you asked a question.

Buy the good stuff for carry or HD, get the decent stuff for range time, shoot "some" of your carry ammo to compare and check reliability.
Key is shot placement and practice. Getting 13.8" penetration from a Federal JHP, vs. 14.1" from a Speer Gold-Dot, vs 12.9" from Cor-Bon, won't matter if the accuracy is there.
Sorry for the long post.
Here's a question:
"If a bullet expands and penetrates 6" and another bullet does not expand, but penetrates 12", which one does more damage?"