11/1/2008

Caliber Wars: The Blame Game

I am frequently asked some variation of this question: "My department issues such-and-such ammunition for our WonderAuto issue sidearms. I’m worried that this caliber/bullet/gun won’t get the job done. What do you recommend?"

My answer has to be predicated on the understanding that I am NOT a ballistics expert. I’ve studied a lot of the terminal ballistics literature, have seen, treated, and reviewed a LOT of gunshot wounds, but I am not an engineer or ballistician. I defer to the works of such leading lights as Duncan MacPherson and Gary Roberts when the discussion centers on the performance of ballistic projectiles in flesh.

However, when it comes to the "performance" of flesh when struck by ballistic projectiles, I do have some significant experience.

And when it comes to the effects of service caliber handgun bullets on flesh and bone, I have formed the confirmed opinion that where the bullet is placed is far more important than which bullet, caliber, or platform you use.   

Dr. Gary Roberts kindly permitted me to reproduce the following photo:

This photo is actually a digital composite of photos of several ballistic gelatin blocks. As you can readily see, all 6 bullets penetrated the FBI required minimum of 12", and not penetrated deeper than 14". All the bullets expanded as advertised.  

Keep in mind that service caliber handgun projectiles create a temporary cavity, but the velocity of expansion of the temporary cavity is much less than that of high-velocity rifle projectiles, and as such do not contribute to wound effectiveness to any real degree. So when we talk about handgun wounding effects, we’re talking about the damage caused by the permanent or "crush" cavity created by the path of the bullet through tissue. 

Wound Track Geometry 

If you visualize the "wound tracks", or the permanent cavities created by each bullet in gelatin as cylinders, we can calculate the nominal surface area—or as I like to call it, the bleeding area—of each wound track by use of the simple formula: 

                        S.A. = pDH  

Where D is the diameter of the permanent cavity, and H is the length of the wound track. D will vary as the bullet expands, but for the sake of simplicity let’s assume D equals the expanded diameter of the bullet. By this method we see that the bleeding area of the 9mm wound is: 

                        B.A. = p x 0.61" x 13" 

                               = 24.9 sq. in.  

And the bleeding are of the .45 ACP wound is 

                        B.A. = p x 0.84" x 13" 

                               =34.29 sq. in.  

The bleeding area of the 9mm wound is 74% the size of the .45 ACP wound, or put another way, the amount of bleeding caused by the .45 ACP bullet is about 25% more than that caused by the 9mm bullet.

In other words, you’re not getting a whole heckuva lot more wounding potential with the .45 ACP than you do with the 9mm. Both calibers, if shot into vital target areas, are going to cause catastrophic damage. But both calibers, if shot into non-vital areas, are going to cause equally trivial damage.  

So what’s the point of caliber wars?