ammunition choices for the handgun
For handguns, the temporary cavity doesn't really do anything(because the projectiles are under the magical ~2000fps mark where temporary cavities+fragmentation can cause bigger permanent wound cavities than the projectile due to ripping and tearing). You're looking at the permanent crush cavity as the only significant means of tissue damage. Energy transfer doesn't mean much. It's the way the energy is transferred through the specific work it does. That is the channel the bullet creates as it physically crushes through tissue.
FMJ vs. Hollowpoint
fmj bullets have a nice round nose up front and don't expand. Essentially, this means they don't crush as much tissue as they pass through. This is because 1) The bullet doesn't expand, so it does work to a smaller frontal area...soo...it does less work
2) It's rounded up front and moves tissue to the side without crushing it, making it's wound channel even smaller.
this means fmj's make a small hole...sooo if they have the same amount of energy, they will make a longer hole to do the same amount of work. This means fmj's will penetrate very far....like....3 feet into tissue far. The small hole is also bad. It means it's a smaller channel for blood to leak out of(takes longer to bleed out) and you're looking at not destroying nearby vessels and tissue that another bullet type would.
Velocity doesn't really come into the picture as a difference between fmj and hp. Both fmj loadings and hp loadings come in a variety of weights and velocities. If you're not going with a hp, wadcutter designs are typically better..they flat surface up front and sharper edges are more prone to crush and bite into tissue. Unexpanded hp's have a similar effect as wadcutters in this regard. Shoot a fmj and shoot a wadcutter or hp at a paper target. look at the neatly punched hole of the wadcutter and hp, then look at the small hole of the fmj with disrupted and pushed aside paper surrounding it. Imagine the same thing happening through very elastic tissue and you'll get an idea of why fmj is a poor defensive loading for any but the worst penetrating cartridges.
Hollow points expand and create a bigger permanent wound cavity. There are different bullet designs, but they pretty much all rely on tissue being forced into the cavity under enough pressure to push outward and expand the nose while crushing the back of the cavity. Some favor expansion while others favor penetration. There's lots of good resources to find what is a good hollow point bullet design.
Best Choices for Self Defense Ammo
FirearmsTactical.com - Web Site Index and Navigation Center
Brass Fetcher Ballistic Testing
CALIBERS -- FBI Ballistic Test Protocol
When hollowpoints expand, it means to do a similar amount of work, it must penetrate less. The fact that penetration can be controlled through expansion is a big safety feature for people downrange that aren't the threat. Limiting penetration to 12-16" makes hollowpoints much safer for your neighbors and other bystanders. This is still of debateable benefit since statistically, you're pretty likely to miss the threat a few times when trying to get a hit or two on them. Things like bone and clothes can clog the hollowpoint cavity and equalize pressure on the nose of it to keep it from expanding. Newer bullet designs are better at resisting this, but some can still fail to expand. When they don't expand, they still perform similar to a wadcutter and much better than a fmj.
How handguns make someone stop
Above, I already talked about handguns wounding mechanism being the permanent crush cavity. Here I'll talk about what it takes to FORCE a person to involuntarily stop. Psychological reasons aren't considered because it's such a huge variable. Some people will stop because of seeing the gun, some will stop because hearing a boom, some will stop once they realize they've been injured, but some will only stop when their body will not go on any more. It's going to be a channel punched into somone that stops them from a handgun. That permanent crush cavity can do 3 main things...
1) Interrupt electrical signals in the CNS
2) Make a person leak fluids
3) Damage the bone/muscle structure
These each have their merits and weaknesses. The first thing to understand is you're probably going to be incapable of aiming for any particular structure of the body. Most likely, you'll have only gross motor skills and tunnel vision which will prevent you from precise shots and only allow for center mass hits.
1) cns-
If you hit the spinal cord or brain, you've stopped the signal from getting to the body....person instantlyish stops. Problem is, the spinal cord is about thumb wide, down the center of the body, and located towards the rear behind lots of body structures. if the person turns or bends, you've got to now take in to account how the spine shifted in position and what's in front of it. The same thing applies for the brain. a headshot from the side is very likely to just crush through the sinus's or the jaw and miss the brain cavity completely if you don't think 3 dimentionally. Shots to the brain also have to penetrate skull...which does a good job of deflection.
In short, CNS shots are very effective, but very unlikely due to the difficulty of placing an accurate shot on such a small target and the phsyical structures that protect them. If they were easy to destroy, we wouldn't be very successful animals in nature.
2) Making person leak-
We're talkin hypovolemia...blood loss shock. You descend through a few stages of shock as you lose blood. I'll copy/paste from the link below to explain and make it easier.
•Class I hemorrhage (loss of 0-15%)
◦In the absence of complications, only minimal tachycardia is seen.
◦Usually, no changes in BP, pulse pressure, or respiratory rate occur.
◦A delay in capillary refill of longer than 3 seconds corresponds to a volume loss of approximately 10%.
•Class II hemorrhage (loss of 15-30%)
◦Clinical symptoms include tachycardia (rate >100 beats per minute), tachypnea, decrease in pulse pressure, cool clammy skin, delayed capillary refill, and slight anxiety.
◦The decrease in pulse pressure is a result of increased catecholamine levels, which causes an increase in peripheral vascular resistance and a subsequent increase in the diastolic BP.
•Class III hemorrhage (loss of 30-40%)
◦By this point, patients usually have marked tachypnea and tachycardia, decreased systolic BP, oliguria, and significant changes in mental status, such as confusion or agitation.
◦In patients without other injuries or fluid losses, 30-40% is the smallest amount of blood loss that consistently causes a decrease in systolic BP.
◦Most of these patients require blood transfusions, but the decision to administer blood should be based on the initial response to fluids.
•Class IV hemorrhage (loss of >40%)
◦Symptoms include the following: marked tachycardia, decreased systolic BP, narrowed pulse pressure (or immeasurable diastolic pressure), markedly decreased (or no) urinary output, depressed mental status (or loss of consciousness), and cold and pale skin.
◦This amount of hemorrhage is immediately life threatening.
http://emedicine.medscape.com/article/760145-overview
Essentially, to get a person into deep enough shock from blood loss to have their body start shutting down, you'd have to force them to lose roughly 2.5-3 quarts of blood from their circulatory system. Blood loss takes time and even if you completely destroy the heart, people have about 10 seconds of useful oxygen and sugar in their brain to function. The faster they lose that 2.5 quarts of blood, the better your chances of not being harmed.
To force them to lose blood, you've got to first hit them somewhere that bleeds alot. See the picture below for a reference of what needs to be destroyed to do that. When you hit something that bleeds, the bigger the tunnel the blood can travel through, the faster blood can leak out through it....but you've got to hit it to begin with. Most things that bleed a lot are deep inside of us. Therefore, a good defensive loading needs to 1) be able to penetrate to the important things and THEEEEEEN 2) be as big a permanent crush cavity as possible to both increase chances of damaging something that bleeds and increase the speed of blood loss.
In this way, a fmj that penetrates deeply enough to reach a vena cava, the heart, or aorta is much more useful than a glaser slug that creates a nice mess of superficial things, but doesn't penetrate effectively to damage things that bleed a lot. Expansion doesn't really matter if it doesn't go deep enough to hit something important.
3) Structure-
Destroying the mechanical parts of the body that enable movement stops that particular movement. This is important, but limited in usefullness. If you hit the pelvis with enough force to shatter the hip's ball and socket joint, that hip's normal movement is altered. It can still move, just not in it's intended way.....and everything else in the body is just fine(unless the femoral artery bleeds out enough for the leaking thing to come in to play). Human body's are amazingly resilient and capable of continuing to function with a large amount of damage. Shoot someone's hip, break a femur, destroy the shoulder and scapula and they'll be impaired, but still capable of attacking you. Especially if they have a firearm or some weapon that allows them to project force beyond their immediate area.
9, 40, 45 are similar in ft/lbs of energy in which they do work, but the slower and heavier 45 will have a larger amount of momentum. It'll make the .45 more useful in continuing through bones and things like that on a straighter course and can give them the edge in structural damage.
As for bullet designs and good defensive loadings that accomplish the above tasks well...
speer gold dot: 124+p & 147 gr
winchester pdx1: 147 gr
Winchester ranger t: 127 +p+, 147gr
federal HST: 124+p, 147, 147+p
hornady critical duty: 135 gr, 135+p
remington golden saber bonded: 124+p, 147(non-bonded have jacket-core separation issues)
cor-bon dpx: 115+p
....I'm sure I'm forgetting a few, but these all will do just fine. The most important factors are that they reliably function in your gun and shot placement.
I wondered if I could get some opinions from the forum on the best ammo and why for self defense. I have a S&W 3913 9mm and have been overwhelmed with all the different info on the internet. Coming to the S&W Forum seemed most appropriate since that is my gun.
