Ballistics

I've written before on ballistics, internal here, external/terminal here, and terminal here.

The science of ballistics is fascinating, and internal ballistics and external ballistics are much more "scientific" than terminal ballistics. You can repeatedly measure the effects of changes on powder charge, primer construction, bullet mass with a good setup. You can accurately map the ballistic path of the bullet as it soars through the air. You can even calculate what a twist rate would do to group size due to bullet imbalance.

What you cannot calculate is whether or not a bullet will stop an attacker. The science of physics exits stage left and the science of biology firmly takes over when we are talking terminal ballistics.

This doesn't stop people from talking about "Taylor's Knock Out Formula" or "Major Power Factor" which are firmly in the realm of physics when describing potential lethality of two different rounds. This is stupid, but people like to argue. Sometimes I think the only reason the internet is so popular is that is allows people to consume porn in private and argue with impunity.

Lethality comes in threes, you need to accurately hit your target. The "center of mass" hold for pistol shooters is fine for a high probability of lethal effects, but it is almost a guarantee that a center mass hit will not "stop" an attacker. To stop an attacker you have to get a central nervous system shot, brain or spinal column, to get a guaranteed stop.

Secondly you need adequate penetration. A 17 caliber lead pellet from an airgun to a human skull will leave a bruise or break skin. A 17 caliber bullet from a rimfire rifle will penetrate the skull and reach the brain if fired at an angle approaching 90 degrees to the surface of the skull.

And lastly, you need tissue disruption. If the bullet is large enough it doesn't have to mushroom or fragment to disrupt enough tissue to kill the animal it hits. But as people who have had nails, knives, and even rebar stuck in their head and live to tell about it, a lack of disruption saved their life. This is where velocity assists in lethality, by providing "hydrostatic shock" at rifle velocities and imparting energy into the projectile to allow deformation or fragmentation even at pistol velocities.

Those who study the impact of bullets into ballistic gelatin can tell you that all things like permanent and temporary wound cavity numbers are not a good indicator of a difference in lethality between rounds of similar mass and energy. What temporary and permanent wound cavities are helpful with is comparing the potential for "bleed out" speed. Bigger holes bleed more, but as experienced hunters will tell you, ballistics gel ain't a living creature with layers of skin, fat, muscle, and bone to deal with.

Lastly, common sense has to have a role, 20 rounds of 22 magnum to the torso is likely to be plenty "lethal" as is 10 rounds of 9x19. But it is a waste of brain power to argue with is "more lethal" because that is like arguing which corpse is "deader." Life and death are binary states. A calculated numeric value based on "energy, momentum, bullet construction, velocity, sectional" isn't very useful at all in determining how a non CNS hit will affect a living animal.