What are the defining features of an "assault rifle"?

See subject line. The phrase “assault rifle” is often bandied about in the media, and I’m wondering what differentiates such a thing from, say, a “hunting rifle” or a “target-shooting rifle,” or a “sniper rifle.” Or any other kind of rifle not named here.

The Army says:
It may be fired semi-automatic like a rifle or full automatic, like a machine gun.
It uses a cartridge between a large rifle and a machine pistol, so that a soldier can carry more ammo during an assault.
Has a large capacity magazine.
Can have a bayonet on it.

Politicians say:
It looks scary.


Except that civilian weapons in the US are not full auto.

Which is why they’re usually called assault-type rifles. They’re kind of like assault rifles, but not really.

They carry on from the characteristics of the first modern assault rifle, the German Stg-44, which combine the properties of a carbine, sub-machine gun and automatic rifle. Wiki has a good list of an assault rifle’s defining properties.

Oh, not by the media, which calls semi-autos “automatics” and anything scary looking “assault rifles”.

You can argue that it is

Gas operated semi-automatic
large magazine capacity

But I’ll point out that my Marlin Model 60 .22 rifle is a gas operated semi-automatic that holds 15 rounds. I’ve already been nearly thrown out of a gun range because I was able to fan the trigger on it so fast that the range officer came running in accusing me of shooting “full auto”.

Here is the definition of Assault Weapon(note: not Rifle) as defined by the previous Federal Law.

Semi-automatic rifles able to accept detachable magazines and two or more of the following:
Folding or telescoping stock
Pistol grip
Bayonet mount
Flash suppressor, or threaded barrel designed to accommodate one
Grenade launcher (more precisely, a muzzle device which enables the launching or firing of rifle grenades, though this applies only to muzzle mounted grenade launchers and not those which are mounted externally)
Semi-automatic pistols with detachable magazines and two or more of the following:
Magazine that attaches outside the pistol grip
Threaded barrel to attach barrel extender, flash suppressor, handgrip, or suppressor
Barrel shroud that can be used as a hand-hold
Unloaded weight of 50 oz (1.4 kg) or more
A semi-automatic version of a fully automatic firearm
Semi-automatic shotguns with two or more of the following:
Folding or telescoping stock
Pistol grip
Fixed capacity of more than 5 rounds
Detachable magazine


The defining characteristics of an assault rifle are:

  1. They have a select-fire function, meaning that with the flick of the safety the weapon can transition from semi-automatic to full-automatic.

  2. They fire a ballistically intermediate cartridge, meaning that it’s not “high-powered”. The 5.56 NATO falls in the middle of the ballistic spectrum, its performance is smoked by genuinely high-powered hunting rifles, but it is hardly .22LR.

  3. It has a detachable magazine.

That’s really all there is to it.

It’s important to note that there is a difference between an assault rifle and an assault weapon.

As noted by others, there is a precise definition for an assault rifle. When semi-auto versions of assault rifles became popular, the media didn’t know what to call them. “Assault rifle” would not be correct, since the civilian versions can’t fire in full-auto mode. So they started calling them “assault weapons.”

Just like to add that although, legally, the difference between semi and fully automatic can be prison time, mechanically the difference between the two is little more than a few small machined parts, specifically the firing pin sear mechanism.

The mainstream media definition is: It looks like a military longarm not a hunting rifle, usually an AR-15 (M16) or an AK-47. That’s about all there is to it for them.

Having said that, looking like one of those means it will be magazine fed from the bottom (as opposed to clip fed from the top) capable of holding 20 rounds or more per magazine, it will use a powerful cartridge bigger than a pistol round (the infamous Thompson sub-machine-gun only used .45 ACP pistol cartridges), and it will be somewhat more compact than a hunting rifle with a slightly shorter barrel and often sliding or folding rear stock.

But mostly, as long as it looks ‘evil’ it’ll get called an assault rifle…

The original military assault rifles have features designed to accomodate the full-auto firing mode. These include a stock which goes straight back rather than curving downwards to minimize muzzle climb; elevated sights because the body of the gun is consequently held lower; and barrel shrouds to protect the shooter’s hands from the barrel heating from sustained full auto fire. The civilian versions derived from them inherited these features even though they’re no longer actually needed.

Just want to point out that the most recent versions of US military assault rifles do not have full auto capability. They are select fire between semi-auto and 3 round burst.

And the media created fear and ignorance.

This. Flat black stocks. Folding stocks. Bi-pods. You know, scary looking stuff.

None of which makes them more dangerous.

Don’t forget “the thing that goes up”.

This is a rather unusual feature copied by no other nation I’m aware of, so I don’t think anyone’s even come up with a name for a weapon that does this.


Burst fire? It’s not as common as automatic fire, but certainly not unusual. Sig has been turning out rifles with a burst fire option since the mid-80s. H&K’s MP5 also has a burst fire option.

I don’t think there is a specific term for select fire weapons with burst. The BATFE considers them to be functionally identical to fully automatic weapons. Most just call them select fire.

I wouldn’t consider fully automatic fire to be a necessary trait of an assault rifle. An AR-15 is still within acceptable use of the term, IMO.

I’d go with

  • mid-sized round, stronger than pistols, less than full-size battle rifle
  • large capacity removable magazine
    and you’re done.

I think fully automatic fire is only a necessity if you’re going for “light machine gun”. And then you’ll need a quick-change barrel to go with it.

edit: all the pistol grip, bipod, bayonet stuff is irrelevant, resulting from the same oversimplication that leads to any armored vehicle with tracks getting called a “tank”, even when it clearly is not one.

And yet, as noted by several posters above, the US military’s own definition of an assault rifle does indeed require the option of automatic fire. The US military doesn’t define an “assault weapon”; it defines an “assault rifle.” According to US Army/Defense Intelligence Agency documents like the one here:

A key requirement of the military definition is that an assault rifle have selective fire capability. You have to be able to select automatic, rather just semi-auto, for it to qualify. An AR-15 doesn’t fit the bill. The manual i linked to above even has a separate category, simply called “Rifles,” for rifles that do not possess the automatic fire capabilities of an assault rifle.

In American lawmaking however, in the 1994 Public Safety and Recreational Firearms Use Protection Act, and in some state laws like those of California, an “assault weapon” is defined in a different way. It refers to a semi-automatic weapon that (often) looks like an assault rifle, and that might possess some characteristics of an assault rifle, but is not a selective fire weapon (i.e., can’t fire auto) and therefore is not an assault rifle under the military definition.

In fact, the Bill creating the “assault weapons” ban specifically banned the possession of a “semiautomatic assault weapon,” and then went on to define such weapons by specifically naming a whole bunch of semi-auto rifles, including the AR-15. You can download the full text of the law here (PDF).

So, while an AR-15 is an “assault weapon” under the definition created by that particular law, it is not an “assault rifle” under the military definition.

It’s worth noting, too, that the 1994 federal law borrowed heavily from the 1989 law passed in California, including listing many of the same weapons by name, and adding the same sorts of criteria for banning other non-named weapons. Some of those criteria had nothing to do with the actual firepower of the weapon, for example, the capacity to attach a bayonet.

Ours (Navy) are M4A1 with semiautomatic and full automatic. You can get them hot enough to cook off a round in the chamber.