Clarification on the "Basic Wound Ballistic Terminal Performance Facts" Thread

[bear22]

Hi all. New to the forums. I am in the market for a primary home defense firearm and have become increasingly interested in an AR over the past few months. I've been reading a lot on M4Carbine.net and other forums, but just recently joined.

I'm doing my best to research and bring myself up to speed on the proper caliber and round for home defense. Originally, I believed the guy at my LGS that undoubtedly a 9mm handgun round is the best projectile and firearm to use for home defense. Since then, through my research, I've learned that his advice is not necessarily correct.

I understand now after reading the Basic Wound Ballistic Terminal Performance Facts thread, among other threads on this forum, what constitutes a round for effective phsyiological incapacitation.

I was hoping someone would be able to clarify two related points from the aforementioned thread. Both areas of question are in bold below.

All projectiles that penetrate the body can only disrupt tissue by these two wounding mechanisms: the localized crushing of tissue in the bullet's path and the transient stretching of tissue adjacent to the wound track. Projectile wounds differ in the amount and location of crushed and stretched tissue. The relative contribution by each of these mechanisms to any wound depends on the physical characteristics of the projectile, its size, weight, shape, construction, and velocity, penetration depth and the type of tissue with which the projectile interacts. Unlike rifle bullets, handgun bullets, regardless of whether they are fired from pistols or SMG’s, generally only disrupt tissue by the crush mechanism. In addition, temporary cavitation from most handgun bullets does not reliably damage tissue and is not usually a significant mechanism of wounding.

Projectile fragmentation in tissue can also greatly increase the permanent cavity size. When a rifle bullet fragments in tissue, each of the multiple fragments spreads out radially from the main wound track, cutting its own path through tissue. This fragmentation acts synergistically with the stretch of temporary cavitation. The multiply perforated tissue loses its elasticity and is unable to absorb stretching that would ordinarily be tolerated by intact tissue. The temporary cavitation displacement of tissue, which occurs following the passage of the projectile, stretches this weakened tissue and can grossly disrupt its integrity, tearing and detaching pieces of tissue. Note that handgun bullets, regardless of whether they are fired from pistols or SMG’s, do not generally exhibit the fragmentation effects produced by rifle bullets. If handgun bullets do fragment, the bullet fragments are usually found within 1 cm of the permanent cavity; wound severity is usually decreased by the fragmentation since the bullet mass is reduced, causing a smaller permanent crush cavity.

Why do rifle rounds fragment and cause temporary crush cavities but handgun rounds do not? I thought it would be more the material of the projectile, the ballistics of the projectile, etc that would determine the crush factor ... not the firing mechanism nor casing.

Apologies if this has been answered elsewhere... I searched to no avail.

Bear

[bear22]

Apologies: I found this in a search ... this tread can be closed.

No, more energy does not mean more lethality. A pistol does not generate significant enough velocity and thus temporary cavitation in tissue to overcome the tissue's inherent elasticity. A rifle is capable of doing massive damage in tissue because it is traveling at a great enough speed that the shock wave overcomes the elastic capabilities of tissue and damages it.

[KCabbage]

It's a matter of velocity paired with proper bullet performance. Velocity around the 2000+ FPS mark is supposedly where the magic starts to happen. However, this must be coupled with a destructive bullet.

There are some transitional calibers such as the .44 magnum that provide some of this additional wounding, but it's probably load dependent.

[bear22]

Thanks. And I'm assuming the velocity is less on a handgun, primarily because if the cartridge was loaded to the point where velocity reached 2,000fps, for example, that the recoil increase would outweigh the benefit of having more accurate rounds on target?

[KCabbage]

Looks like you beat me to it. So yes, as you see velocity has a major role in this. But, not all high velocity loads are created equally. For instance, a .223 load traveling at 2900 FPS that doesn't fragment or expand will most likely leave nothing but a .22 caliber hole in its target. Now take that same velocity paired with a bullet that fragments or expands once entering the target and you have quite a impressive wound.

Still, even with a good bullet at high velocity, 12"+ of penetration is highly recommended. Shot placement is also a crucial element.

[KCabbage]

More or less.

Typical velocities from service caliber handguns:
9mm 147 gr = 1000+/- FPS
9mm 124 gr. +P = 1200+/- FPS
40 S&W 180 gr. = 1000+/- FPS
45 ACP 230 gr. = 890+/- FPS

Pick a reliable platform that works best for you. Don't get too wrapped up in caliber as they all tend to perform well with proper load selection.

[bear22]

Thank you. I understand there are various reasons why you'd choose a respective firearm over another for home defense application.

I own a Glock 17 Gen 3 and am happy with it for the home defense application I would likely require.

I've been interested in an AR for a while - admittedly first due to the allure of the weapons, but more recently for expanded and future home defense application.

I've read The Chart and various threads through out this forum and have a pretty good idea of the direction I want to go. I just have to decide my budget, when/where I can get training and exactly which brand I want to go with (I am considering BCM, DD, Noveske, Colt, and LMT but still don't get the finer differences!)

[jmoore]

Why do rifle rounds fragment and cause temporary crush cavities but handgun rounds do not? Bear

Welcome to the list - from a relatively low-level newb:)

A simple start to the answer (not the end-all, btw) is that fragmentation is often correlated with both having a cannelure, as well as increased velocity. As many 5.56 rounds fit both criteria, there is a greater likelihood of fragmentation, thus leading to multiple wound channels and increased tissue crush. As barrel length drops, so does velocity (all other factors kept constant) - and the tendancy to fragment also decreases. Thus - less likely to happen in handgun shootings.

Another topic you might want to research (both here, and online) is hydrostatic energy - an oft-used and misused term when applied to various firearms. You will find that higher velocities, especially if the rounds hit organs with capsules, tend to generate the temporary cavity you mentioned (and dramatic damage to boot:) Doc can follow up on details:)

john

[bear22]

fragmentation is often correlated with both having a cannelure, as well as increased velocity.

Thanks! I understand all of what your are saying, with the exception of the quote above. I've googled and most posts that are showing up do show a correlation of cannelure to fragmentation - but none of what I found explains why.

Cannelure is the crimping of cartridges, correct? How would that induce fragmentation?

[bear22]

So I was thinking about it and my logic could be way off, but I'm guessing that because cannelure is the ring that allows for crimping, having that ring would weaken the jacket at that point, potentially creating a sitution where fragmentation is more likely to be induced?