Guns, guns, and different guns

On a very basic level, all guns are the same. I'll let Homer Simpson explain:



However, they diverge rapidly from there. In all the discussions following various mass shootings, the anti-gun (or gun control, if you will) crowd has jumped straight to policy with very little understanding of how guns are different from each other. There are many calls to "ban all those automatic and semi-automatic guns". Of course this warrants immediate contempt from 2nd Amendment advocates (or pro-gun, if you will) because it reveals a clear unfamiliarity with the world of firearms. "Semi-automatic" seems to be a loose term for "really powerful" and I'm not sure what automatic is even supposed to mean in this context ... but maybe "military powerful"? At any rate, these terms have concrete meanings and they matter to those who understand them. In the interest of dialog, it's important that both sides use proper terminology.

Automatic means the user pulls the trigger once, and bullets keep flying out until s/he lets go. These are what we usually see in our action movies, and include the M-16 and M-4 most commonly used by our military in war zones. They are able to fire hundreds of rounds per minute, in principle an M-16 could empty its 30-round clip in just a few seconds. Larger belt-fed models like the M-60 can sustain that rate much longer. Not all automatics are big or powerful; Uzis are a prime example of a small automatic fire weapon. These guns are largely illegal in the civilian population due to the 1986 Firearm Owners' Protection Act.

Semi-automatics require the user to pull the trigger once per bullet. That is the only fundamental differentiation from the group above. On a per-bullet basis, these guns can be just as powerful as those above. For example, high-powered hunting rifles are available in semi-automatic. The AR-15 is the predecessor to the M-16 and M-4 above and shares their firepower. However, many are much smaller: the Glocks used by many police forces and civilians, or even this tiny Beretta.

There are also guns that require additional input from the user to load the next round. Old single-action revolvers required the user to pull the hammer back to turn the cylinder. Bolt-action (common for hunting rifles) requires the user to explicitly eject the previous cartridge and chamber the next round.

What actually damages a human? It's the energy transferred by every bullet that hits them. This energy can be quantified: it is the "muzzle energy". For example, an M-16 uses a standard NATO round that is rated around 1800J, while a 9mm Glock might use a .380 ACP round rated around 300J. Even big-boy handgun ammo like the .45 ACP and 10mm auto top out around 800-1000J. As this trauma radiologist points out in a well-circulated piece in The Atlantic, the impacts from these are worlds apart.

In addition to the damage caused per bullet, there's the matter of how fast accurate shots can be fired. The AR-15 looks similar to military guns precisely because it was the original, designed to do the same things. It was built with the ability to take a large magazine, to be aimed easily over long distances, and to recoil minimally so the process can be repeated as fast as possible. While not a fully automatic, an AR-15 still has an effective fire rate around 1 shot per second. Since each bullet causes so much damage, the 20 or 30 in the magazine can be targeted at that many separate targets. Because the weapon is so much more accurate and easy to aim, a skilled user can reasonably expect to deliver a lethal shot from 500 yards, vs maybe 50 yards for the Glocks used by police. Given a crowd, a skilled operator could probably kill a dozen people in under 30 seconds. This combination of power, range, and accuracy makes it hard for a crowd to get to safety. It allows a shooter to set up in Mandalay Bay and rain death onto a concert hundreds of yards away.

Interestingly, recoil is a big enough issue in handguns that the FBI requested lower-speed ammunition for their Glocks outfitted with .40 S&W ammo specifically to improve their weapons handling. Because properly used rifles eliminate recoil to such a huge degree, they can retain their rapid fire rate and high power.

It's easy to see why mass shooters are drawn to "assault rifles". Interestingly, the AR-15 (or non-Colt-brand variants thereof) used in many shootings does not qualify under the US Army's definition since it lacks selective fire capability (it's only semi-automatic). The definition doesn't matter. The function does. It fires a highly lethal NATO round that was designed to penetrate 1/8" steel armor and steel helmets at 500 yards. There's no reasonable need for that level of firepower outside of a war zone. Upping the ante, the highest firepower available is the 18,000J of the .50 BMG round, used by the readily available Barrett M82, with effective range over a mile (and confirmed longest deadly shot at 2.2 miles). Thankfully it makes a poor "assault" weapon because it weighs 30lbs and rounds cost about $4 apiece. But, it would be highly effective and lethal from a perch.

Attempts at legislation can be obviously tricky. Attempts to outlaw ammunition above a certain muzzle energy will impinge on big-game hunters. Shooting a moose, elk, bear, etc, requires serious firepower. Limiting specific weapons or ammunitions will just cause manufacturers to create slight variants of existing models. The trick is to find the right feature, or combination of features that eliminates weapons with mass offensive capability. I think the right ideal model is some combination of limiting muzzle energy in combination with semi-automatic weapons. For example, suppose you can't buy a semi-automatic weapon that fires rounds over 1000J. This ends up being unenforceable through the combination of a custom "weak" round for the semi-auto weapon and the creation (or existence) of a bolt-action gun taking the same format. There's some precedent already via the definition of all illegal destructive devices, which does include any ammunition with great than 1/2" caliber ... but the law mostly focuses on explosive devices, rockets, etc. There's a bit of a "you know it when you see it", but that can't translate to law. Maybe a solution is to eliminate all semi-automatic rifles in an attempt to limit the rate at which damage can be done?

The 1994 Federal Assault Weapons Ban was an attempt to classify what an "assault weapon" is, but its guidelines seem to have a lot of loopholes or misses. For example, rifles had to meet at least two of:

• Folding or telescoping stock
• Pistol grip
• Bayonet mount
• Suppressor or threaded barrel to accept one
• Grenade launcher

It's pretty easy to imagine an AR-15 variant without suppressor threads that doesn't meet the above definition. This illustrates that even with the appetite to make changes, and even if an AR-15 variant is explicitly disallowed, it would simply require the manufacturer to make a new model with a minor cosmetic change that would not be covered under the legislation. Perhaps the approach could be that new models must be opted into legal status, and existing models can be placed on disallowed lists?

It's also important to remember that mass shootings make up just a few percent of all murders. Handguns are responsible for the majority, but they rarely make headlines because they usually just kill one or two people at a time. The goal of limiting "assault rifles" is just to limit the carnage in special cases with deranged shooters. Any new laws need to address issues while not unduly burdening citizens. Proposals like arming teachers (and training them, and spending taxpayer money on more guns, ammo, etc) definitely seems to fail that. But anything we can try for "cheap" that might improve our outcomes should be tried, measured, evaluated. And then we build from there.