[GBullet]

Actually, momentum plays a huge role:

When a bullet passes through tissue, the tissue stays close to the surface of the bullet for a short ways, then it begins to separate. The tissue separates from the bullet surface after the bullet has imparted enough outward, or radial, momentum (there's that word again) to the tissue.

Watch a boat as it moves quickly and you will see the water thrown by the bow away from the boat. The boat moves forward, but the water is tossed to the side. The boat has imparted momentum to the water (technically it's a change in the momentum of the water). The same thing happens with bullets and tissue.

Here's why this momentum is important...The radial momentum given to the tissue by the bullet makes the temporary cavity. For a given tissue, the size of the temporary cavity depends on the bullet's energy, area and shape.

Put in simple terms, in tissue a non-expanding bullet will be at it's best with a wadcutter shape.

 

[GBullet]

jamullins,

You're right that normal sized pistols are not going to equal M16 rifles anytime soon. Interestingly, the .223 (5.56mm) is generally considered by arms designers to be comparable to the 9x19mm from a wound standpoint within 300-400m. That is to say that the .223 FMJ is assumed to always create a wound at least equal to a 9mm NATO FMJ.

The paradox of pistols is that convenient size and effectiveness are opposites. Even if you do develop a compact handgun/cartridge that is similar in performance to a rifle, the chamber pressure has to remain safe anywhere that it may be used. It must also not wear out the pistol too fast.