What Is An AR 15?

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What is an AR 15? Developed by Eugene Stoner in 1957, the AR 15 rifle was built to meet the needs of soldiers following WWII. Although many have mislabeled the “AR” as meaning assault rifle, it actually stands for ArmaLite Rifle which was the manufacturing company that held the first rights of the design. It wasn’t until 1959 that ArmaLite sold the rights to the AR 15 to the current owner Colt. In order to be considered an AR 15, the firearm must perform basic functions on its own without effort from the user. Upon pulling the trigger, the firearm needs to fire a single cartridge and remove the used case from the chamber. It must also load an unused cartridge into the chamber from the magazine, cock the hammer and prepare to fire a fresh round. There are two operating systems available for AR 15s, the direct gas impingement system and the gas piston system.


Direct Gas Impingement System

In a standard direct impingement system, hot gases and carbon from the barrel are vented into a gas tube that travels through a hole on the barrel. These gases then travel back toward the receiver, where all of the critical moving parts (such as bolt and carrier) are located, using their pressure to push the bolt carrier backwards toward the stock of the rifle. The hot carbon dirties the moving parts inside the receiver which can cause the parts to break down overtime. In order to keep the system running efficiently, it requires extensive cleaning and maintenance.




Gas Piston System

With a gas piston system, the hot gases and carbon go down the barrel and enter a piston chamber that drives a one piece rod back which actuates the bolt carrier. The gases are redirected forward out of the chamber and away from all critical moving parts. Unlike the direct impingement, the piston system eliminates the carbon build up in the receiver in turn extending the life of the rifle. In order to keep the system running efficiently, it requires very little cleaning and maintenance. The gas piston technology was first seen by Mikhail Kalashnikov’s AK 47. Although they are similar, there are a few main differences.

The Great Debate

Proponents of the direct impingement (DI) system say that it fires with more accuracy and has been proven reliable in battle situations. It has also been said that it has easy to replace parts and is easier on the wallet with its prices. On the flip side, disadvantages have been pointed out by the opposing side with arguments of malfunctions due to the hot dirty gases fouling up the critical moving parts, and the time in maintenance it takes to keep the DI gun running properly.


Proponents of the gas piston system are quick to fire back that a piston system has a higher level of reliability because it keeps the dirty gases out of the receiver, and away from the critical moving parts with its cleaner, cooler operation. This extends the life of the gun and reduces chances of malfunctions which is crucial in a battle situation. The entire gas system is accessible from the front of the block for easy maintenance and cleaning and the forward motion of the sleeve on the plug scrapes away residual carbon for an even cleaner system.


Whatever your stance on the subject, the AR 15 platform has become a staple firearm for military, civilian and law enforcement use. With the technology developed by Stoner, the AR 15 will continue to adapt to the needs and wants of today’s shooter. Now that we have clearly defined what an AR 15 is and the different systems it can operate with, find a friend and go to the range to put them to the test yourself!

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