Why the AR-15 is different, and what that means

So, this is where your favorite gun-savvy lefty explains some things.

Lately, we’ve heard a LOT about the AR-15, which is the civilian and semi-automatic version of the M-4 used by our military. The rifle is ubiquitous today; until recently, I’d bet 90% of America was within 20 miles of a store that would sell them one this afternoon. They’re not that expensive, and they’re absolutely terrifying — it’s not for nothing that they’re the weapon of choice for mass shootings.

The the AR-15 is really just one of a class of magazine-fed, semi-automatic rifles chambered for a particular bullet type (the proper term is “round” or “caliber”) usually abbreviated to “5.56”. The proper name is 5.56 x 45mm NATO.

It’s not an especially beefy or powerful round in the realm of rifle rounds; most folks hunt deer with far larger calibers. It’s relatively small size, though, makes it very, very well suited for rapid fire because it produces so little recoil (“kick”). Sure, you almost never see a fully-automatic AR used for crimes, but it hardly matters because a semi-automatic version will fire as quickly as you can move your finger.

That small round packs a tremendous punch — especially since it’s usually shot from a platform that allows or even encourages the shooter to keep firing.

So in this context, take a look at this piece by a Parkland area radiologist, speaking about the wounds from the MSD shooting:

What I Saw Treating the Victims From Parkland Should Change the Debate on Guns.

This is from a radiologist with plenty of exposure to handgun wounds. They tend to be relatively simple and manageable, and if the bullet manages to avoid something critical like the aorta or the heart, the patients tend to survive:

In a typical handgun injury, which I diagnose almost daily, a bullet leaves a laceration through an organ such as the liver. To a radiologist, it appears as a linear, thin, gray bullet track through the organ. There may be bleeding and some bullet fragments.

I was looking at a CT scan of one of the mass-shooting victims from Marjory Stoneman Douglas High School, who had been brought to the trauma center during my call shift. The organ looked like an overripe melon smashed by a sledgehammer, and was bleeding extensively. How could a gunshot wound have caused this much damage?


Routine handgun injuries leave entry and exit wounds and linear tracks through the victim’s body that are roughly the size of the bullet. If the bullet does not directly hit something crucial like the heart or the aorta, and the victim does not bleed to death before being transported to our care at the trauma center, chances are that we can save him. The bullets fired by an AR-15 are different: They travel at a higher velocity and are far more lethal than routine bullets fired from a handgun. The damage they cause is a function of the energy they impart as they pass through the body. A typical AR-15 bullet leaves the barrel traveling almost three times faster than—and imparting more than three times the energy of—a typical 9mm bullet from a handgun. An AR-15 rifle outfitted with a magazine with 50 rounds allows many more lethal bullets to be delivered quickly without reloading.

I have seen a handful of AR-15 injuries in my career. Years ago I saw one from a man shot in the back by a swat team. The injury along the path of the bullet from an AR-15 is vastly different from a low-velocity handgun injury. The bullet from an AR-15 passes through the body like a cigarette boat traveling at maximum speed through a tiny canal. The tissue next to the bullet is elastic—moving away from the bullet like waves of water displaced by the boat—and then returns and settles back. This process is called cavitation; it leaves the displaced tissue damaged or killed. The high-velocity bullet causes a swath of tissue damage that extends several inches from its path. It does not have to actually hit an artery to damage it and cause catastrophic bleeding. Exit wounds can be the size of an orange.

Let’s quantify this. Wikipedia can help; let’s compare the 5.56 to the most popular handgun round, 9mm.

Firearm ballistics are a complicated area that people LOVE to argue about, but the gist of the system boils down to the bullet’s mass and the amount of energy pushing it forward. The bullets are measured in grams (or sometimes another unit called grains); we talk about energy in terms of muzzle velocity and downrange energy. The difference, as the author notes, isn’t small:

  • A 5.56mm round involves a fairly tiny bullet (~ 3-4 grams, so more than a penny and less than a nickel) moving at about 900 m/s, and will deliver on the order of 1,800 joules downrange.
  • The 9mm pistol users a heavier bullet (7 to 8 grams, so twice as massive as the 5.56), but it’s moving far slower: usually the neighborhood of 350 or so m/s, so the energy delivered when it his something is also far lower (~ 500 joules).

An AR-15 is also engineered to shoot quickly, and shield the user from almost all the recoil. I’ve shot one several times; it’s very easy to shoot, and very easy to shoot quickly without losing the target. Frankly, it’s easier to stay on target with an AR than it is with most 9mm pistols.

This is why the wounds the Parkland physician saw were so much worse, and why mass shootings end with so many dead: because it’s easy to get a weapon that will fire very many of these very lethal rounds very quickly. And the NRA likes it this way.

Oh, one more thing: Gun violence is clearly a public health problem in the United States, but we don’t study it. Why?

The Centers for Disease Control and Prevention is the appropriate agency to review the potential impact of banning AR-15-style rifles and high-capacity magazines on the incidence of mass shootings. The agency was effectively barred from studying gun violence as a public-health issue in 1996, by a statutory provision known as the Dickey Amendment.

Why is it banned? Because the NRA doesn’t want it studied. Think on that.

6 thoughts on “Why the AR-15 is different, and what that means

  1. The M-16 where the M-4 originated was originally designed in 308. Ironically the rifle design was not built to kill but to injure as many enemy combatants as possible in belt buckle missions. The military eventually moved to the 5.56 cartridge due to carry capacity. That the military continues to develop more lethal rounds, 458 socom, 300 AAC to operate in the M-4 platform speaks to this very fact.

    I own a few AR rifles varieties 22lr, 223/5.56, 308, 300 AAC, 300 Win Mag. All of which could kill a person or several people more effectively depending on the range. But all are quite lethal, including the subsonic 22lr, which shoots at a lower velocity than your coveted 9 mm round, and actually is my favorite of the bunch.

    What makes the AR so deadly is the myriad of options that one can outfit and tailor to their own shooting needs. The modular efficiency of the platform makes it so that it costs very little for relatively high performance on an individual level. Sights, optics, trigger weights, springs, bolt carrier groups, stocks (bump fire or not) fore ends, flash and sound suppressors and ammunition choice ( both caliber and grain).The efficiency and now dependability of the, DI/piston floating barrel and BCG make the AR platform second only to maybe AK and that is debatable.

    That said, it is a slippery slope to judge a firearm solely on the trauma inflicted in a mass shooting. It is just as valid to judge a race by the number of mass shooters that make up that population. Perhaps banning white people from owning AR 15s would do the trick? Should we also ban pickup trucks for their propensity to kill people in DWI manslaughter cases versus say a compact? How about we ban the mentally ill too while we are at it? Hell let’s just ban everything to make us safer. I mean why stop at guns? Soft drinks, alcohol, caffeine all pose a serious health crisis. One could argue sitting on your ass in front of computer and a smartphone are a bigger health crisis in this country. Ban the inter webs. You know studies show bicycle seats cause testicular cancer, must ban now, do it for the children.

  2. That’s a bunch of data points in search of an argument, though. I mean:

    1. Yes, you can get an AR in other calibers. But there’s reason 5.56 is the overwhelming favorite: its relatively modest recoil makes it easy to shoot A LOT, and — as the radiologist notes — it’s plenty lethal. Nobody is going to go on a shooting rampage with 458 SOCOM.

    2. .22LR is in no way, shape, or form as lethal as .556. Don’t muddy the water. The ballistics are pretty freakin’ clear here: .22LR delivers about 10% of the downrange energy as 5.56. You’re not going to get the kind of wound channels that 5.56 delivers because there’s not enough energy there.

    3. The AR as a platform isn’t the whole picture. Sure, you can go all Tactical Tommy and kit your rifle out with insane accessories, but the point of my post is that AR + 5.56 is a particularly awful combo for mass shootings. And, unsurprisingly, it appears to be the platform of choice for such events.

    4. This isn’t a “slippery slope.” It’s a stone fact that an AR is a killing machine. As evidence, I offer Stoneman, Vegas, and any number of other public shootings.

    5. It’s interesting you bring up DWI, because we as a country have absolutely reckoned with our impaired driving problem in a way we refuse to do with firearms. Given what I presume your position to be here, then, maybe that’s not the best example for supporting your argument.

    6. Which brings me to this: What IS your position here? That we do nothing? That we just accept mass shootings as a fact of life?

    We have a lot to do legislatively. Universal background checks need to happen, and yeah I do mean closing the gun show loophole. Licensing and liability insurance needs to happen. And it took me most of my adult life to get here, but frankly I no longer see any legitimate reason for semi-automatic magazine fed rifles to be legal.

  3. A. You posit that the 5.56 cartridge and the AR in tandem is a killing machine, and use the pathology provided by the radiologist as evidence. As I posted, the AR was never desiigned to be a killing machine. Nor was it designed to shoot a 5.56. It was designed to wound and the addition of the 5.56 was added to increase carrying capacity, not for lethality. Your original argument is flawed, Irrespective of the opinions of the doctor you quote.

    B. In fact a 22LR is as lethal as a .223/5.56 . They both can kill a person quite effectively. The. 22LR is a famous asassination round. I have killed a deer with both a subsonic 42 gr no less, and a supersonic 70 gr 223. The point is that the 223 is not evil. It is not anymore or less deadly than a 22lr regardless of the velocity it leaves the barrel. Many a mob hit has been carried out with a 22LR. It is fact. C. Point taken. The AR and the 5.56 is terrible when used in mass shootings. I think that no one will argue that any gun and ammunition used in a mass shooting at a school or concert or a government office is bad. I think where we differ is to put the blame on the weapon and ammo. Banning legal ownership of any firearm is unconstitutional. And we can go round and round on qualifiers but the bill of rights is crystal clear. D. The slippery slope is not whether or not the AR is a killing machine. It is. All firearms are killing machines. They are made to kill. However, I have several, and not one has ever killed a person. It is not the instrument that kills it is the person using it. You writing that the AR and 556 is a killing machine is not the issue at hand and you damn well know it. You are suggesting that these items should be banned because a bunch of crazy fucks have used them for slaughter. E. Actually, I think DWI is the perfect analogy. Vehicles are not banned when sick people get in them and kill others. Buicks were not banned when Teddy Kennedy got hammered and drove his car off a bridge into chappaquidick and left his knocked up gal to drown. F. My position is that the constitution is crystal clear on the rights of people in this country. When people abuse these rights we should not infringe on the rights of law abiding citizens as a reaction.This is not a safety issue to be regulated by the CDC, nor is it a question of lethality of firearms. When people legislate and use tragedy as an excuse to gut the constitution the only thing that happens is that our society loses rights never to see them again. You have written about this many times on this blog (911/patriot act for example) and yet now you want to ban firearms due to a tragic event? This is not logical. How long before this tactic is used to defeat all rights?

  4. So what I hear you saying is:

    1. “It wasn’t even DESIGNED to be 5.56! Plus, everybody says it was designed to wound, not kill!”

    The original planned round for the AR platform is entirely irrelevant.

    Gun-nut chatter about how the 5.56 is meant to wound, not kill, is very difficult to square with what actually happens when a 5.56 round hits someone’s center mass, as described by the radiologist.

    So far, you’re not gaining ground.

    1. “In fact a 22LR is as lethal as a .223/5.56”

    Absolute, complete, unadulterated TWADDLE that is beneath you. That you CAN kill with a .22 doesn’t mean it’s AS lethal as a high-power rifle round. I mean, there’s MATH here: 5.56 delivers an order of magnitude more energy downrange.

    Moreover, the increased lethality of 5.56 over handgun rounds — all of which are ballistically superior to .22 — is the whole point of the linked article. It cites actual wound characteristics, which absolutely trump this ridiculous assertion.

    1. “Banning legal ownership of any firearm is unconstitutional”

    Again, you’re just wrong here. Fully automatic weapons are effectively banned, for example. Further, the amendment in question actually refers to “well regulated” in the fucking text. So miss me with this NRA bullshit.

    1. “All firearms are killing machines” is, again, a bullshit position. The point here is that semi-automatic high capacity military rifles — of which the AR is an excellent example — are especially suited for killing lots of people quickly in a way that a Remington 700 deer rifle is not.

    This is not a thing that people need to be able to do. We are paying a ridiculous price so that ammosexuals can get a woody playing tactical tommy with guns they have no reasonable use for.

    1. Yes, DWI is a great example. In response to a problem, we increased regulation and oversight. I’m glad you agree.

    2. Crystal clear isn’t what you think it is here. Also, the CDC doesn’t regulate; they provide data. By this throwawway line, though, I suspect you mean to say you don’t think gun deaths should be studied as the public health problem they clearly are.

    “Now you want to ban firearms.”

    No. Now I want to ban a specific subset of firearms. Keep your pistols. Keep your shotguns. Keep your bolt-action or pump rifles. No one will be defenceless againt their imagined armed intruders; toddlers will remain free to kill more people with guns in the US than terrorists do.

    “How long before this tactic is used to defeat all rights?”

    Now THERE’S your slippery slope!

  5. I think you may want to look up the definition of lethal. I know you are the wordsmith here but just in case you did not know it means “sufficient to cause death” Something isn’t more lethal, you can’t qualify lethality, it is like being kinda pregnant. Putting a bullet into someone is generally lethal. It does not matter if one bullet can do so with much greater force. Bullets that travel at high velocities are not necessarily more lethal. You fucking know this because you shoot 9 mm and you know they are known for in-and-out wounds, which do not generally knock someone down. The 556 is the same and this is why the US military continues to seek out other rounds.

    My comments on the origination of the platform and the round were there to point out that the military who ordered this rifle, whose business is to eliminate other soldiers built the platform to maime and not kill. It is completely relevant to your argument that lower powered firearms are somehow more “acceptable”. And if it does not discredit your basic premise, AR+223 is evil and should be banned, it should certainly inform you that your statement is flawed at the very least. At best it is a scare tactic, used for propaganda to trample on the Second Amendment and to push this agenda.

    I really have no opinion on whether the CDC should study mass shootings? I guess you could call it insanity, or mental health support failure that fuels these murder sprees. Though this does not jive with your assertion that mass killings are due to the availability of high capacity rifles.

    The Second Amendment clearly states that we have the right to bear arms. A well regulated militia is not the qualifier to that right. I do not know how you are going to argue against that? Your machine gun argument actually orove my point. We will keep classifying firearms as too dangerous and eventually get to no firearms. Trending towards zero.

    I think anyone who has shot using a bumpfire technique or a fully automatic system would know that this does not make you more lethal with a rifle. The military has removed full auto function on standard M-4 to make their soldiers more accurate and more effective.

    As for DWI, they did not ban drinking, or driving, they penalized those who did both. This is not what you are suggesting here. You are quite clearly saying to ban guns and that is going to magically stop mass shootings. And though you may be saying ban some guns, what it leads to is a ban of all guns that are lethal. And well you now know that all guns are lethal. So that is a problem.

    I will never agree to this as my family fled tyranny by people who grabbed guns and much more. This is not theory to me.

  6. I think you may want to look up the definition of lethal. I know you are the wordsmith here but just in case you did not know it means “sufficient to cause death” …

    Seriously? This is the hill you want to fight for? You’re splitting hairs because your position is untenable, and it’s beneath you.

    The ENTIRE FUCKING POINT of the linked article is the drastically higher level of damage — and, yes, lethality — that a 5.56 wound creates vs. handgun rounds. That’s game, set, and match, buddy.

    Whining that a well-placed, close-range .22LR might also kill someone is completely fucking beside the point when we’re talking about arms most useful for killing a bunch of people quickly. How many mass shooters are using .22LR, Edgar? None? Which countries use .22LR as their main infantry weapon? Also none?

    You’re just going to have to let the “5.56 was designed to maim, not kill” bullshit go, because it’s just that: bullshit. It’s on you to find a respectable citation for it, but 30 seconds with Google will show you it’s a myth. It was about weight, so you can carry more ammo, and about controllability. You and I have both shot 5.56 and 7.62, and you and I both know how easy it is to keep 5.56 on target vs. the bigger round.

    Though this does not jive with your assertion that mass killings are due to the availability of high capacity rifles.

    Mass shootings are not due ENTIRELY to the availability of high cap high power guns — you also need a crazy person — but if any fool with $800 couldn’t leave a gun show with an AR we’d have a lot fewer such shootings. I don’t know what’s hard about that.

    The Second Amendment clearly states that we have the right to bear arms. A well regulated militia is not the qualifier to that right.

    Fortunately, no one is relying on you for legal advice.

    Firearms are regulated already. They should be MORE regulated. Substantial regulation is possible without material abrogation of the gun-humpers’ favorite amendment.

    I think anyone who has shot using a bumpfire technique or a fully automatic system would know that this does not make you more lethal with a rifle

    You’ve got to be fucking shitting me now.

    And though you may be saying ban some guns, what it leads to is a ban of all guns that are lethal. And well you now know that all guns are lethal. So that is a problem.

    This is known as the “slippery slope” logical fallacy and, again, you’re smarter than this.

    I will never agree to this as my family fled tyranny by people who grabbed guns and much more. This is not theory to me.

    Oh, for fuck’s sake.