Back when I first got into guns, I had a very limited understanding of wound channels. My basic premise was: if a bullet is going under 2000 FPS, the wound tract is roughly the size and shape of the bullet. If a bullet is going over 2000 FPS, the wound tract gets proportionally bigger.
Over the past month or so, I've been doing as much second-hand research as I can (i.e. not shooting gel blocks myself, but looking at what others have done). A lot has been done, and publicly posted, in the last several years. The ability to see many different tests done in slow motion instead of in a final still image has led to a much different understanding. However, I don't have simple numbers anymore, as I believe the equations have gotten much more complex.
From what I can tell, there are three primary wounding mechanisms:
Crush damage can be increased by expansion, fragmentation, or tumbling; at a loss of penetration.
Cavitation is the effect that a bullet's velocity, weight, diameter, and shape have on the transfer of energy through the target. A light, slow, small, round-nosed bullet will have a very low cavitation. A large, heavy, fast, blunt bullet will have a high degree of cavitation. This is why a shotgun slug, even moving at less than 2000 FPS, will have a massive cavity. As to shape, this is where something like a fluted bullet comes into play.
The process of deformation or destabilization (i.e. tumbling) can also lead to cavitation damage. This tends to create a wider bulge in the wound tract, but not necessarily a wider overall wound tract than the more permanent properties of a bullet.
Fragmentation can happen on impact (i.e. Glazer Safety Slug), during terminal ballistics (i.e. a 55-grain 5.56mm FMJ), or even before the round is loaded from the factory (i.e. a shotshell). What fragmentation does is amplify the effects of the other two wounding mechanisms, but often for a very shallow distance. Fragmentation increases crush damage by increasing the surface area of the round. Fragmentation increases cavitation damage by helping to tear elastic tissue that would otherwise have snapped back into place.
At least, this is my current understanding of how bullets (or pellets) affect the target. It's helping me build my new plans for what types of ammo to load for self-defense. (Put simply, buckshot in shotguns, FMJs in AR-type rifles, and fluted bullets in handguns).
Did I miss something? Get something wrong? Are there better numbers for the above?
Over the past month or so, I've been doing as much second-hand research as I can (i.e. not shooting gel blocks myself, but looking at what others have done). A lot has been done, and publicly posted, in the last several years. The ability to see many different tests done in slow motion instead of in a final still image has led to a much different understanding. However, I don't have simple numbers anymore, as I believe the equations have gotten much more complex.
From what I can tell, there are three primary wounding mechanisms:
- Crush damage
- Cavitation damage
- Fragmentation damage
Crush damage can be increased by expansion, fragmentation, or tumbling; at a loss of penetration.
Cavitation is the effect that a bullet's velocity, weight, diameter, and shape have on the transfer of energy through the target. A light, slow, small, round-nosed bullet will have a very low cavitation. A large, heavy, fast, blunt bullet will have a high degree of cavitation. This is why a shotgun slug, even moving at less than 2000 FPS, will have a massive cavity. As to shape, this is where something like a fluted bullet comes into play.
The process of deformation or destabilization (i.e. tumbling) can also lead to cavitation damage. This tends to create a wider bulge in the wound tract, but not necessarily a wider overall wound tract than the more permanent properties of a bullet.
Fragmentation can happen on impact (i.e. Glazer Safety Slug), during terminal ballistics (i.e. a 55-grain 5.56mm FMJ), or even before the round is loaded from the factory (i.e. a shotshell). What fragmentation does is amplify the effects of the other two wounding mechanisms, but often for a very shallow distance. Fragmentation increases crush damage by increasing the surface area of the round. Fragmentation increases cavitation damage by helping to tear elastic tissue that would otherwise have snapped back into place.
At least, this is my current understanding of how bullets (or pellets) affect the target. It's helping me build my new plans for what types of ammo to load for self-defense. (Put simply, buckshot in shotguns, FMJs in AR-type rifles, and fluted bullets in handguns).
Did I miss something? Get something wrong? Are there better numbers for the above?