CCW Weekend: Physics, Ballistics And The Birdshot Myth

The humble shotgun suffers from an absolute deluge of myths, misconceptions, lies, and outright hogwash to a degree unmatched by the myths, misconceptions, lies and outright balderdash pertaining to other firearm types.

One of the worst of these tropes that never seems to die is one of stacking one or two shells of non-lethal (or more accurately, less-than-lethal) ammunition ahead of anti-personnel ammunition in the magazine.

Typically, the idea goes that you load a bean bag round, rubber slug, or birdshot as the first or even the first two shells and then buckshot or lead slugs for the rest.

The reason is usually to have a “warning shot,” in other words a munition you can smack a home invader with to give them the idea that they broke into the wrong rec room, but without killing them.

Some people even perpetuate the idea that a non-lethal first shot makes a lethal follow-up shot justifiable since the person was clearly given a warning they did not heed, meaning the threat was clearly real.

It sounds great in the movies.

WATCH:

 

But that’s not really how it works in real life.

First of all, use of a gun – at all – is only legally permissible if the threat is actually real; “it was only birdshot, Your Honor” is not a legal defense.

Furthermore, we have the “warning shot” as a concept. If the threat wasn’t serious enough to actually shoot the person, it wasn’t serious enough to shoot them. In other words, if the threat isn’t serious enough to give them every pellet in a shell of 00 buck, it’s not serious enough to shoot, period.

Then there’s the issue of less-lethal ammunition and their powers of persuasion. Now is it the case that rubber buckshot or slugs, or a bean bag round, or for that matter birdshot, is anything you want to get hit with? Obviously not.

But is it the case that it’s going to stop a person?

If someone is determined enough to do you grave harm, they may need a lot of convincing. Buckshot and slugs are known to be convincing; others are not.

There are plenty of reports of police officers that had to put multiple shells of buckshot into suspects to stop them, so it’s not the case that 00 buck is even a guaranteed one-shot-stop, and if even buckshot doesn’t do it 100 percent of the time, what good is birdshot going to do?

To reinforce the concept, let’s bring a bit of physics into it.

Force equals mass times acceleration. In other words, the amount of force a projectile delivers depends on the mass of the projectile as well as the velocity to which it is accelerated by the charge of propellant.

Acceleration stops once the projectile leads the barrel. Since this planet isn’t a vacuum (though make no mistake, sometimes living here sucks!) a projectile begins to lose velocity to wind resistance and gravity.

The aerodynamic properties of the projectile – specially the ballistic coefficient, but let’s not get too far into the weeds – determine the rate at which velocity is lost. The greater the mass and the higher the ballistic coefficient, the slower the rate of loss.

This is why rifle bullets remain lethal at distances past 1,000 yards and why shotgun pellets become ineffective within 100 yards.

Herein layeth the problem with birdshot.

A solid projectile, having more mass, will lose momentum (and energy) at a slower rate than a bunch of tiny projectiles.

Birdshot is literally a whole bunch of tiny round pellets (No. 8 is .09 inches in diameter, and weighs .0024 oz) and has a pathetic ballistic coefficient. In other words, it sheds velocity and energy after it leaves the barrel at a staggering rate.

It takes several hundred foot-pounds of force to break bone, and about 100 ft-lbs to penetrate skin. While birdshot leaves the barrel with enough energy to do lethal damage, it loses it fast, and even after a few feet is no longer lethal.

For visual reference, here’s a gel test of birdshot: 

 

For a bit more detail, here’s a slow-motion gel test using 1-oz No. 8:

 

 

As you can see, birdshot does do impressive superficial damage but it is, again, only superficial. All the energy is transmitted into the target in the first few inches of ballistic gel.

For a bit more fleshing out (pardon the pun) ballistic gel is not a perfect medium for testing efficacy of projectiles on human targets, but it does give you an idea of its efficacy in proportion. The rule of thumb is a 2:3 ratio; every 3 inches of penetration in gel is 2 inches in human tissue.

However, the first few inches are skin, fat and muscle; in other words nothing vital. If a projectile can’t get through 4.5 inches of gel, such as in the second video, it’s not going to penetrate more than an inch or possibly two in human tissue.

That means a superficial wound, only. While perhaps that might dissuade some people from carrying out murderous designs, it’s not going to stop everyone.

And thus begging the question that if a situation is serious enough to warrant use of a gun, why would you bother?