I posted a Facebook status yesterday in jest over a caliber discussion. I was really surprised to see how many people came out of the woodwork to offer input. I was also surprised to see that some people thought I was ignorant and failed to see the humor. They didn’t read the entire thread. Allow me to take this opportunity to clear the air and tell you where I really stand.

I am not a ballistics expert. I am not a medical expert. I am an NRA certified instructor as well as a student and teacher of self-defense using a pistol. My knowledge on this topic comes from countless hours of research using sources I think are credible as well as my understanding of physics. My position on this topic comes from a practical perspective and is not based on one factor.

Now that we’ve got that out of the way, I’ll tell you what I posted.

Kid in one of my classes: “Mike, why do you carry a .45? Those bullets move so slow I can see them.”

Big Mike: “Would you rather be hit by a pebble traveling 100 miles an hour or a baseball sized rock at 50 miles an hour?”

“Kid in one of my classes” is a classmate, not a student. And yes, the analogy is exaggerated, but it’s funny. If you didn’t laugh, you really need to pull whatever it is out of your sphincter and lighten up.

And then the old caliber debate started. You’ve heard them all before (my rebuttals).

  • I shoot a .45 because they don’t make .46. (Well… they DO make something larger than a .45. It’s called a .50. And Demi Moore shot one in each hand in Charlie’s Angels.)
  • . 45ACP, because shooting twice is just silly. (Well… you could shoot twice if that round didn’t just pound the eff out of your shooting hand.)
  • I like to call them “flying ashtrays.” (Don’t forget… cigarettes kill.)

The debate is old. I imagine it comes from the same place that the Harley vs metric cruiser debate comes from. The place I’m referring to is jealousy and inadequacy.

The truth is that today, both arguments (yes, even the motorcycle one) are irrelevant.

Ballistics is a science. Like any other science, advancements change the landscape over time. In the case of ballistics, the science has rendered the caliber debate a useless conversation that only allows someone to show his or her ignorance.

The fact of the matter is that stopping power is not about cavity size. Yes, a large cavity will stop someone sooner than a smaller cavity. However, in the case of self-defense uses of a handgun, that cavity won’t prevent an attacker from inflicting serious bodily harm or killing his or her victim. Countless determined bad guys in FBI and police encounters have demonstrated that they are capable of fighting even after receiving several shots creating huge cavities and/or ripping right through the body. Relying on soft tissue damage for immediate stopping power assumes that one of two vital organs is hit.  A shot to the heart or brain may very well immediately incapacitate an attacker, but even the most experienced shooters will not be able to make such a shot in the high stress environment of a self-defense scenario.

Soft tissue damage is just not a good measure to determine the effectiveness of a round with respect to self-defense.

Immediate stopping power is derived from deposition of energy.

Handgun cartridges transfer the gun powder’s stored chemical energy into kinetic energy of a bullet that is then deposited into a target. Kinetic energy is equal to one half of the traveling object’s mass (in our case, a projectile) times the velocity squared. There is also a shockwave traveling in front of the projectile as it rapidly displaces the air in its path.


The projectile’s kinetic energy is transferred to the target when the mass of the target decelerates it. Energy from the shockwave is transferred to the target as well. Enough energy deposited into the body of an attacker rapidly enough will disrupt his or her body’s electric impulses and nervous system signals. Shut down enough signals and muscles can stop working. Make the right muscles stop working and the attacker can go into cardiac arrest. Cardiac arrest can result in immediate expiration.

Friction is one of two processes by which one object in motion transfers its energy to another. It can also transfer its energy by way of collision. Friction and collision are two transfer of energy processes present when one mass decelerates the other.

Hollow point bullets are effective at depositing their kinetic energy because they stop inside the target. Modern hollow points are designed to expand when they enter soft tissue at a certain velocity. When the bullet expands, its surface in the path of travel is increased. It encounters more friction.  The larger the surface area of the bullet the more it’s interaction with the soft tissue becomes a collision. Once the bullet has deposited all of its energy into the soft tissue, it stops. A hollow point bullet that deposits all of its energy into a body of soft tissue does not exit the body.

But what about the energy of a big slow moving bullet versus a small fast moving one?

Go back to the kinetic energy equation. For a big bullet to posses the same energy as a small one, it must travel at a velocity equal to the velocity of the smaller bullet multiplied by the square of the ratio of smaller bullet’s mass to the larger one’s. The larger bullet can move considerably slower than the smaller one and still possess the same amount of energy. In the right light, you can actually see a .45 caliber bullet leave the muzzle of a handgun in real time.

Ammoguide.com collects data from hundreds of sources to determine average muzzle energies of a wide range of loads within certain calibers. The average muzzle energy of various calibers can be quite surprising. For the purposes of this discussion, we will focus on popular semi-automatic calibers.

Ballistic Comparison Summary Results

Caliber  Muzzle
 (Avg. f.p.s.) 
 (Avg. ft-lbs.) 
 (Avg. gr.) 
 (Avg. grs. H2O) 
 .380 Auto (9mm Kurtz) 891 183 105 90 13.5
 9mm Luger (Parabellum) 1143 344 121 437 15.9
 .40 S&W 1033 394 167 369 21.6
 .45 ACP 835 356 230 2 28.7

The difference between the average muzzle energy of a 9mm Luger and a .45 ACP bullet under the commercially available range of loads is less than 3.5%. 40 S&W packs the biggest punch at 12.7% more average muzzle energy than a 9mm Luger. .380 is the weakest of the rounds and just over half the average muzzle energy of a 9mm Luger.

Distance, or range, of the shooting is not a factor. Deceleration due to air resistance is negligible inside the distance self-defense encounters occur. Extensive research has found that 90% of police encounters occur within 15 feet and the majority of civilian self-defense encounters occur within two arm’s length.

Furthermore, research by Florida State criminologist Gary Kleck determined that in only about 3% of all self-defense encounters is a firearm actually discharged. In only a few incidents every year is the attacker actually shot. Death of the attacker is statistically rare. Stopping power is largely psychological in nature.

Yes, caliber has very little to do with stopping power and the effectiveness of a self-defense firearm.

A self-defense firearm in any caliber 9mm or larger should be chosen based on several factors:

  • How well can you conceal it?
  • Can you carry it?
  • Can you draw it from holster and put rounds on target before an attacker hurts you?
  • Do you like to shoot it?

A lot of times, the choice boils down to nothing more than “I like it.”