Breaking Down the AR-15


I’ve never owned a rifle, and for the gun debate I don’t have a personal dog in the fight. However, I am interested in public safety, appropriately balanced against the legitimate rights of gun owners. This article is a layman’s view of assault weapons, looking at the pros and cons of restrictions. My conclusions and opinions are shared here. Your mileage may vary. Of the 310 million guns in the U.S., somewhere between 8.5 and 15 million are assault weapons according to the National Rifle Association. This number is about 3 to 5 percent of all guns in circulation. Other estimates are lower, but data is not maintained for the various classifications of weapons.

The term “assault weapon” and “AR-15 semi-automatic rifle” have become standard terminology in the news. Assault weapons can include handguns and shotguns, but this article focuses on rifles.

Basic gun components are shown above. The charging handle “cocks” the rifle, making it ready for use by loading a first round (single unit of ammunition) into the firing chamber. The receiver is the guts of the gun. For AR-15 style firearms, the receiver is divided into upper and lower parts that can be easily separated. The lower receiver is where the serial number of the gun is found.

The other components in the diagram relate to what makes a rifle an “assault weapon.” The specifics of this term vary somewhat from state to state, but the now-expired federal assault weapons ban (from 1994 to 2004) defined an assault weapon as a semi-automatic with a detachable magazine and additional features, described below, that were felt to mimic a military-style rifle.

A semi-automatic gun shoots one bullet with each pull of the trigger. This can be done rapidly because with each shot the next round of ammunition is automatically loaded into the firing chamber. Meanwhile, a detachable magazine allows quick reloading. The gun user simply pulls out an emptied magazine and pushes in another that is ready to go.

For an experienced shooter, a 30-round magazine (a typical size) can be emptied in eight seconds or less and a fresh detachable magazine inserted in two seconds or so. While some state laws limit magazine size to ten or fifteen rounds, one hundred round magazines are available.

The expired federal law held that any two of the following features would make a semi-automatic rifle with detachable magazine into an illegal assault weapon:

Folding or telescoping stock: A folding stock makes the weapon easier to transport. A telescoping (or collapsing) stock moves in and out to adjust the rifle to whatever is most comfortable for the user.

Pistol grip: A pistol grip can provide a more natural way of holding the weapon, in comparison to the traditional straight grip.

Bayonet mount: A bayonet mount allows a blade to be easily attached to the front of the rifle, which can be critical in military close-quarter combat.

Flash suppressor or threaded barrel designed to accommodate one: A flash suppressor is a device that attaches to the muzzle (front of the gun barrel). It disperses and cools the gas discharge from the weapon, thus reducing the potential that the shooter will be temporarily blinded in low-light situations. Secondarily, it also reduces the flash that allows an enemy to detect the weapon’s position.

Grenade launcher: Due to regulatory requirements under the National Firearms Act, explosive grenades are difficult and expensive to obtain. Grenade launchers are not found in typical civilian semi-automatic rifles.

One other term is important. An assault rifle is not the same as an assault weapon. These similar terms can make discussions quite confusing, especially because one term is often used when the other is meant. An assault rifle is a fully automatic firearm, meaning that one pull of the trigger will continue to fire bullets until the trigger is released or all ammunition is expended. It is also called a “selective fire” weapon because it can be set to fire in up to three ways: “single fire” (one bullet at a time), “burst” (two or three rounds fired in quick succession), and “full auto” (machine gun mode). Ownership of assault rifles is tightly restricted in the U.S. In actual use by the military and police the fully automatic mode is often not used because accuracy is compromised.

Gun rights activists feel that the term “assault weapon” is a misnomer and prefer the term “modern sporting rifle.” They claim that the true objection to some rifles is that they “look scary” because they have been derived from military weapons rather than American hunting traditions. They argue that the particular features defining an assault weapon do not make it inherently more dangerous than any other semi-automatic rifle with detachable magazine and feel that the special features that distinguish an assault weapon are largely cosmetic rather than dangerous.

These last arguments appear to have merit. In terms of mass murdering innocent civilians, a semi-automatic rifle with a detachable magazine appears to provide the core benefit, and the additional features such as telescoping stock and pistol grip do not appear to add appreciably to the ability of a gunman to inflict lethal injury.

How lethal are assault weapons? Assault weapons, using slightly varying definitions, have been banned in California, Connecticut, Maryland, Massachusetts, New Jersey, New York, and the District of Columbia. (Assault pistols are also banned in Hawaii.) So far, these restrictions have withstood court challenges.

How rifles such as the AR-15 work can be best understood visually. A two-minute CNN video is available here and illustrates the rapid-fire capabilities.

An add-on device currently in the news is a “bump stock.” This device essentially turns a semi-automatic rifle into a fully automatic one like a machine gun. Bump stocks are legal in many parts of the country, but some jurisdictions have banned them or limited their use.

Fully automatic mode using a bump stock is less accurate than single-fire due to the recoil of the gun. However, mass murderers seem to be most interested in overall carnage in public spaces rather than particular victims.

In 2010 the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) evaluated bump stocks and determined that they did not violate a ban on automatic weapons. They now appear to be revisiting this issue, though Congressional action would be more definitive. A six-minute video that shows an AR-15 in action, with and without a bump stock, is available here.

Some gun rights activists point out that multiple-fire mode can be achieved without a bump stock or similar device, by a technique using a pants belt loop to hold a user’s thumb in a particular way. While true, this is a cumbersome approach that would not provide much utility to a mass murderer.

Semi-automatic weapons, even without conversion to an automatic-style mode, can fire quite rapidly. They can be accurately characterized as extremely lethal (in the wrong hands). However, gun rights activists appear correct that the distinction between “assault weapons” and all semi-automatic rifles with replaceable magazines appears tenuous.

One could make the argument that all semi-automatic rifles with a replaceable magazine are extremely dangerous, yet a ban on an entire class of weapons would raise significant Second Amendment concerns and would not align with the cultural traditions in much of the country.

In evaluating whether additional gun restrictions are appropriate, the utility of semi-automatic weapons for completely legal uses must be recognized. An argument from an AR-15 gun owner is available here.

In balancing public safety against gun traditions, one western state has put emphasis on the gun magazine rather than the gun itself.

The gun regulations of Colorado: In 2012, a gunman at a movie theater in Aurora, Colorado, armed with a shotgun, 100-round semi-automatic rifle, and handgun, left twelve dead and seventy injured. The next year, Colorado added to its gun laws. These changes did not ban assault weapons but did ban large capacity magazines accepting more than fifteen rounds of ammunition. This approach of focusing on the amount of ammunition in a replaceable magazine and not the gun is unique among states.

The time difference for a mass shooter in changing the gun magazine every one hundred rounds versus every fifteen rounds, realistically, is only a few seconds, but those few seconds can be the difference between life and death for innocent victims.

Personal conclusions. Like all difficult social issues, arguments and passions exist on both sides of the gun debate. After looking at the details of semi-automatic weapons, I’ve come to the following thoughts:

Assault weapons bans: The country is too diverse to implement an assault weapons ban on a national basis. With the prior federal ban, existing weapons were grandfathered, manufacturers were able to ramp up production prior to the implementation date, and workarounds with minor redesigns were fairly easy. A state-by-state approach is consistent with the concept of federalism.

Expanding the definition of assault weapon: The distinction between “assault weapon” and “semi-automatic/replaceable magazine” weapon seems reasonably unimportant, which some might argue is support for a broadened definition of assault weapon. While reserving decision making to the separate states, this appears to be an aggressive step that could have significant opposition.

Bump stocks: The video link provided earlier that shows a bump stock in action seems to unequivocally call for significant limitations on this device, and other devices that essentially change a semi-automatic weapon into an illegal machine gun.

Magazine size limits. The approach used in Colorado to focus on limits to magazine size (rather than banning assault weapons) appears to be a reasonable step for states that wish to address important safety concerns while only impacting minimally on legitimate gun use.

There are many additional potential gun regulations, including waiting periods, age limits, regulation of ammunition sales, and training requirements for the most lethal weapons. The next few months will determine what additional actions are underway in balancing cultural and Second Amendment traditions against legitimate concerns for public safety.

For more information, the Giffords Law Center to Prevent Gun Violence, even while advocating for additional gun restrictions, is an excellent general resource.