The AR-15 assault rifle is a hot topic lately, with legislators looking to ban or limit sales due to its latest reported links to gun violence. Even the Bureau of Alcohol, Tobacco, Firearms, and Explosives is trying to ban a very popular type of ammunition for it. However, the AR-15 is arguably the most popular sporting rifle in the country. When you start talking about the AR-15, an argument will start about which is the better rifle: the AR-15 or the AK-47/74. While both have their good and bad points, I prefer the AR series for a couple of reasons.
One being, the M16/M4 is the standard battle rifle for the U.S. Armed Forces and federal, state, and local law enforcement. In most cases, parts for the M16/M4 are interchangeable with the AR-15. This means that during a major event like a natural disaster or a zombie outbreak, parts, magazines, and ammunition could be found just about anywhere.
AR-15 | An Assault Rifle of Choice
There are some important differences between the military and civilian versions of the rifle and we’ll talk about those, as well as the differences found among the AR family of weapons.
Before we get into the AR-15, I feel it’s important to know a little bit about the M16/M4 and its history.
A Brief History of the AR-15
We’ve all seen the M-16 on television or in the movies. For years, most people assumed that the AR-15 is the semi-automatic version of the M-16. In 1959, ArmaLite sold its rights to the AR-15 to Colt. The AR designation was kept, but contrary to popular belief, AR does not stand for Assault Rifle. It meant and still means Armalite Rifle. The AR-15 was first adopted, in 1962, by the United States Air Force for their security police; the AR-15 received the designation M16. The U.S. Army began to field the XM16E1 in 1965, with the majority of them going to the Republic of Vietnam Army and the newly formed Airmobile Divisions, chiefly the 1st Air Cavalry Division.
There were a lot of problems with the first M16s, mostly failures to eject spent rounds that caused the weapon to jam. A good friend who fought in Vietnam told me that when he first used an M-16, it jammed constantly and usually at the absolute worst time.
The problem was traced to the powder used in the round, as well as some other reliability problems. These were fixed and the M-16A1 was born. The A1 was followed by the A2, and it was that model that was later developed into the M4; the currently issued rifle is the M4 carbine. The M4 carbine has a three-round burst firing mode, while the M4A1 carbine has a fully automatic firing mode. Colt’s Manufacturing LLC retained the AR-15 designation and offered it for sale to civilian and law enforcement markets as a semi-automatic version of the M-16.
Semi-automatic AR-15s for sale to civilians are internally different from the fully-automatic M16. Outwardly, they appear nearly identical, with the upper receiver being only slightly different (having an area milled out for clearance). Internally, however, they are apples and oranges, being the hammer and trigger are of a different design. The bolt carrier and internal lower receiver of semi-automatic assault rifles are milled differently so that the firing mechanisms are not interchangeable. This was to satisfy ATF requirements that civilian weapons cannot be easily converted to full-automatic. In the late 1970s and early 1980s, modifications to the AR-15 were rampant, with “Drop In Auto Sear” or “lightning-link” conversions to fully automatic. However, these were very straightforward modifications, and unless using registered and transferable parts made prior to May 19, 1986, are now illegal.
In 1986, The Firearm Owners Protection Act (Public Law 99-308) redefined a machine gun to include individual components that can be used to convert a semi-automatic firearm to full-automatic. I cannot stress this enough. If you convert an AR-15 to full automatic and you get caught, you are going to prison. The ATF’s Firearms Enforcement Division takes this very seriously.
Having said that, there are parts that are interchangeable, and having them installed on your AR-15 does not make it a machine gun under federal law. The full auto bolt and bolt carrier are interchangeable, and having one in your rifle is legal. One thing to note on the interchangeability of parts, the AR-15 comes in two variants: Commercial and Mil-Spec. Over the course of this article, I’ll point out the differences between AR-15 and M16/M4 parts and Mil-Spec vs. Commercial. Regardless, the various types function in the same way.
Figuring Out Which AR-15 Is Best for You
The AR-15 consists of three major components: the upper receiver, the bolt and bolt carrier, and the lower receiver.
The upper and lower receiver are held together by two pins. Pushing the rearmost pin out will allow the upper receiver to tilt forward for field cleaning while pushing both pins out will allow the upper and lower assemblies to be separated.
There are two basic operating systems for the AR-15, Direct Impingement and Gas Piston, with the most common being Direct Impingement. All of the ones I own are Direct Impingement.
Direct impingement is the original technology used in the M16 and its variants devised by Eugene Stoner in the 50’s. Propellant gas from the fired round is bled through a small hole located in the barrel, this gas is then channeled through a very small tube where it is fed to directly contact (or impinge) the bolt carrier. At this point, the gas is pushed to the rear of the rifle, forcing the bolt carrier back where the spent case is extracted and ejected. As the bolt carrier moves rearward it pushes the buffer back, compressing a spring. It is then pushed forward by spring-loaded action, and strips an unspent round from the magazine, loading it directly into the chamber of the barrel. I purposely fired hundreds of rounds through one of my ARs without cleaning it to see if I could induce a malfunction and never could.
A gas piston is the same operation used by the AK-47. While it is more or less the same as direct impingement systems, there are a few differences. Firing a round again feeds propellant gases into the barrel. But instead of being forced into a tube as it is in a direct impingement system, it is contained in a separate cylinder. This cylinder holds a piston. As the gas moves the piston, it, in turn, pushes the bolt carrier rearward to extract the spent rounds and feed in the new round. The bolt carrier is pushed forward to the closed position by a spring, just as with direct impingement.
Which is better is another question that is sure to start an argument. My only comment is the military uses direct impingement and the vast majority of the civilian AR-15s are direct impingement.
Let’s examine a direct impingement AR-15 in detail.
Starting from the front and working our way back, the example shown below is a stripped AR-15 that uses a 300 AAC Blackout, 7.62×35mm cartridge. Other than the caliber, the component parts and operation are the same as a standard AR-15 in .223/5.56.
Starting with the barrel, the end — unless the barrel is target crowned as the .308 AR-10 shown above — will be threaded 1/2×28, which is standard for 5.56/.223. It will vary with other calibers. The one shown is for a 300 Blackout and is threaded 5/8×24. This particular barrel is stainless steel.
The flash suppressor shown above is a shorty muzzle brake and is also threaded for a suppressor. Next are the gas block and gas tube. Under the gas block, there are holes in the barrel for the gas to escape. Some gas blocks are adjustable; these adjustments allow you to control the amount of gas and in turn control cycling and operation. The one shown is not adjustable.
The gas tube and barrel are covered by the forward hand guard. There are a huge number of options for the hand guard and it is really up to you. One thing to keep in mind is where the gas block is and the length of the gas tube. This will determine the handguard style that you can use.
Next is the upper receiver. There are a number of options but they are all more or less the same. The barrel is attached to the upper receiver. It contains the ejection port, in some cases the forward assist, charging handle, and the bolt, and bolt carrier. Some upper receivers have an integral carry handle and some have rails.
Next are the bolt, bolt carrier, and charging handle. This is an example of the difference between the full auto bolt carrier and the civilian version. As shown below there is a notable difference between the two.
The charging handle is used to move the bolt carrier rearward to charge the weapon. There are a number of options for the charging handle. Shown is a standard one alongside one with an extended ambidextrous latch.
The upper receiver is not considered a firearm and therefore is not controlled. You can order one and have it shipped directly to your home regardless of the length, but anything less than 16 inches is considered a Short Barreled rifle when mounted on a lower receiver with a stock. This does not apply to an AR-15 pistol with a SIG style brace. A Short Barreled rifle is controlled by the National Fire Arms Act (NFA) and must be registered, with all of the applicable paperwork and tax stamp.
Simply having a short barreled upper is not in itself illegal. However, if you have a short barreled upper and a standard 16-inch barreled AR-15 and you are caught with both, you could be in a lot of trouble. The standard AR-15 can easily be converted to a Short Barreled rifle that you have not registered. There is a case law that reflects the ATF’s position on this subject.
Upper receivers are functionally all pretty much the same. They can be made out of metal like aluminum, either cast or billet, titanium, or a composite like carbon fiber. They can be purchased as a stripped unit, assembled, or as a complete upper as mentioned above.
In part two of this series, I’ll be discussing the lower receiver and the AR’s ammunition.
Know why the AR-15 rifle is the most popular gun in the U.S. in this video by Seeker:
Remember, the AR-15 and M-16 rifles look so much alike in their outward appearance, but the internal operation of these rifles are quite different. AR-15s are designed in such a way that the firing mechanism of the firearm can’t easily be converted to full auto. This is important, especially for civilian-owned rifles. It’s a requirement by the ATF clearly for precautionary measures on the non-military use of firearms.
What do you think about the AR-15 and its design? Share your thoughts in the comments section below!
Editor’s Note – This post was originally published in March 2015 and has been updated for quality and relevancy.