Originally Posted by peacefulgary
...Low energy rounds just suck, like a 35g .25 auto from a 2" barrel, which will only give you around 60 ft. lbs. of energy.
Or a 60g .32 auto from a 4" barrel, which only give you around 120 ft. lbs. of energy....
Actually, the reason these cartridges will tend to perform poorly is not a matter of energy as energy. Rather, these are small caliber bullets making small holes, and with low sectional density and low momentum making for poor penetration.
Originally Posted by peacefulgary
...High energy rounds are just more effective than low energy rounds (when it comes to quickly stopping aggressive humans) regardless of the velocity, IF the bullet stays inside the target and dumps all of its energy in to that target...
 You can't separate energy from velocity because energy is a function of the square of the velocity.
 But "energy dump" is meaningless.
 See post 51 for the back-up for my opinion.
 The effectiveness of a cartridge for self defense is related to the amount of tissue damage and resultant blood loss. And that is related to the diameter of the hole (permanent wound cavity) made by the bullet as long as it penetrates sufficiently.
Originally Posted by Bob Wright
...The bullet's relative performance on living animals, large or small, is a good representation of the bullet's effect on human beings...
Yes and no. As the animal begins to approach the size of a human, a necropsy (postmortem examination of a non-human subject) will probably provide a fair amount of useful information about the bullet's effect on tissue, but not necessarily its effectiveness for self defense.
The physiological effects of any particular amount of tissue damage would be vastly different for a 200 pound man compared with a 20 pound mammal. The man has greater depth, density and amount of musculature, heavier bones, larger organs and a much greater blood volume. If, for example, a bullet damages 0.5% (by weight) of a 20 pound animal's total tissue mass (about 1.6 ounces), that amount of tissue damage is only 0.05% of the 200 pound man's total tissue mass. And even 2% of the dog's tissue mass is still only 0.2% of the man's.
Understand that there are four ways in which shooting someone stops him:
- psychological -- "I'm shot, it hurts, I don't want to get shot any more."
- massive blood loss depriving the muscles and brain of oxygen and thus significantly impairing their ability to function
- breaking major skeletal support structures
- damaging the central nervous system.
Depending on someone just giving up because he's been shot is iffy. Probably most fights are stopped that way, but some aren't; and there are no guarantees.
Breaking major skeletal structures can quickly impair mobility. But if the assailant has a gun, he can still shoot. And it will take a reasonably powerful round to reliably penetrate and break a large bone, like the pelvis.
Hits to the central nervous system are sure and quick, but the CNS presents a small and uncertain target. And sometimes significant penetration will be needed to reach it.
The most common and sure physiological way in which shooting someone stops him is blood loss -- depriving the brain and muscles of oxygen and nutrients, thus impairing the ability of the brain and muscles to function. Blood loss is facilitated by (1) large holes causing tissue damage; (2) getting the holes in the right places to damage major blood vessels or blood bearing organs; and (3) adequate penetration to get those holes into the blood vessels and organs which are fairly deep in the body. The problem is that blood loss takes time. People have continued to fight effectively when gravely, even mortally, wounded. So things that can speed up blood loss, more holes, bigger holes, better placed holes, etc., help.
So as a rule of thumb --
- More holes are better than fewer holes.
- Larger holes are better than smaller holes.
- Holes in the right places are better than holes in the wrong places.
- Holes that are deep enough are better than holes that aren't.
- There are no magic bullets.