Caliber, velocity, energy, relating to damage Theory

[Dibbs]

My experience is that 45ACP, while a century of empiric evidence espouses it a capable anti-personnel round(JMB himself designed it as such, and built the 1911 around it, as a delivery system for the round) it has lousy penetration characteristics, just short of anemic. .44 Mag, quite the opposite, but bear in mind you are using 3 or 4 times the powder load on approximately the same projectile.

9mm has excellent penetration characteristics, by comparison to 45ACP, using about 65 to 80% as much powder to drive a bullet about half the weight and cross section. The greatest benefit of 9mm is it's overall recognition and acceptance as an efficient round, and all the fine pistols which have been chambered in the caliber. The higher capacity of 9mm mags, IMO, gives a superb advantage to the caliber, as well as it's accuracy enhancing lower recoil.

But it's still a buck-dancer's choice, as to which to use, for personal defense.

 

[bdickens]

Fact is, handguns are very poor manstoppers in the first place.

"A pistol is what you use to fight your way back to the rifle you never should have left behind in the first place. "

But, various law enforcement agencies all over the place have had satisfactory results with any and all of the typical service calibers available.

So, I think it is really a waste of time to get involved in these silly caliber wars. Pick a reliable pistol, load it up with a good round and don't worry about it.

 

[2zulu1]

<minor rant>

I am going to step back and somewhat retract my, "kinetic energy is king" comment. I am an engineer by profession and kinetic energy is a quantity I have been using since high school physics. I like kinetic energy, it's what does the work in a collision and it gives you a nice idea or cap on how much work/damage is possible, but that really gives you very little information on what that work/damage will look like and if it's useful work. It also means a lot more to me than just that one simple number since I understand implicitly at this point where it came from and the other stuff that number drags along in the background, but ultimately you can't simplify terminal ballistics to just kinetic energy or just momentum.

Energy and momentum are inseparable quantities. P = mv and KE = 1/2 mv^2. So if a bullet has a particular mass (m) and velocity (v) then there is nothing you can do to effect that bullets momentum (P) without effecting its kinetic energy (KE) and vise-versa. When you really get into the dynamics of high velocity collisions (ie graduate level college course type work) you solve these problem using every bit of information you can, the projectile's mass, velocity, shape, & material properties; the target's shape and material properties, impact geometries and deformations in all their glorious vector quantities, etc. There is no simple answer that only uses energy or only use momentum as you might see in a high school level physics course. They have made a bunch of simplifying assumptions to teach basics principals. These first year physics problems are a very poor reflection of most real world collision especial such complex realities as bullet target interactions.



This dynamic finite element model of a jacketed AP round hitting an aluminum plate and has alot more inputs than just momentum or just energy. Look at all that geometry and how it deforms both elastically and plastically. Imagine if the bullet had the same mass and velocity (same energy and momentum) but the core was soft lead instead of the hard tungsten modeled, the outcome would have been very different. And this model is relatively simple given it involves only simple solids (no strain rate dependencies) with elastics and plastic deformations. Now if we make the target a biological target with non-Newtonian fluids, gases and vaporized liquids, and strain rate dependent solids and the math starts to get hard. We do terminal ballistics a disservice by trying to simplify it to just one number. We all do it, myself included, but we need to stop IMHO. It just ain't that simple.

</minor rant>

I understand the difficulties of applying the correct wounding formulae in service calibers. My understanding (simplicity) that upon collision and during the bullet's deformation, is that of kinetic energy absorption, the process of turning kinetic energy into heat energy.

"The reason that kinetic energy and damage are not always correlated is that dynamic damage is not due to energy absorption, but to stress; force per unit area."

Is this your understanding?

 

[Dibbs]

"Damage Theory", ( IMO, almost an elegant way of putting it), isn't a precise art, and has to rely, for a large part, on empiric evidence. Debriefings, where the shooter said "I shot him, he fell down, and did not get back up." for instance. Even with reams of data supporting the efficacy of 45ACP, and 9mm Luger, who's to say if an equal amount of soldiers had been provided with the obviously more powerful and almost prohibitally expensive 44 Magnum, that they would not have had a different result/ viewpoint ?

Once again opinion, but if you are trying to decide what you want to select as your personal caliber, I would advise trying many, first, then picking one which works well for you, practicing, and getting good with that chosen caliber.

 

[Texasgrillchef]

Even within a specified caliber, we know that bullet design/type also impacts the amount of damage done to the “target” as well. Thus it’s possible for a smaller caliber bullet to do more damage then say a larger caliber FMJ.

 

[Trunk Monkey]

Even within a specified caliber, we know that bullet design/type also impacts the amount of damage done to the “target” as well. Thus it’s possible for a smaller caliber bullet to do more damage then say a larger caliber FMJ.

Ya think?