How the AR-18 influenced a generation of service rifles

Armalite made its name with the AR-15 which would go on to be the M16 and the M4 and rule the American military market. Armalite sold the AR-15 design to Colt, who became the supplier of military rifles to the United States military. However, Armalite was still in business and needed to continue producing rifles. This led to the AR-18, a new rifle designed to be an affordable 5.56 assault rifle with tons of modern features. 

Although it wasn’t a complete failure, the AR-18 didn’t succeed at the time. Yet, Armalite had reignited the same flame that made the AR-15 successful. The AR-18 would go on to be one of the most influential assault rifles in the world – it just took it 50 years. 

The Cold War and the AR-18 

The Cold War significantly influenced rifle design, with the majority of countries settling on one of three designs: The hybrid piston and direct impingement design implemented by the M16; the long-stroke gas-piston rifles in the AK series; and a much smaller group of rifles that used an AR-18-style short-stroke gas design. 

The AR-18’s gas-piston system positioned the gas piston over the barrel with a block near the end that siphoned gas off a fired round to press the piston backwards to cycle the firearm. The bolt would go running backwards as the piston struck it, causing empty cases to extract and eject. The bolt compressed a spring and when it reached max compression the spring pushed the bolt forward, loading the next round and locking the breach. 

(The AR-18 wasn’t the first short-stroke gas-piston system. Guns like the M1 Carbine and the Russian SKS had used the system before.)

Cold War guns influenced by the AR-18 include the Japanese Howa Type 89, the Taiwanese Howa Type 65, the Steyr AUG, and the British SA80 family. Although the AR-18 was influential during the Cold War, it was always overshadowed by the AK and M16. 

Then the 2000s happened. 

An evolution or recognition

Between the Cold War and the Global War on Terror, the AR-18-style gas system languished. The most notable firearm to use the system, in that period, was the HK G36, but other than, the AK and M16 families reigned supreme. 

In the 2010s, we saw the rise of suppressors, very short carbines, and a demand for automatic fire from rifles. Even though the AK and AR-15 families could handle these requirements, but there was always a compromise. 

On the one hand, the AK’s long-stroke gas-piston guns were never going to be as accurate as other designs’ and didn’t offer advantages to the Western world. On the other, the AR-15’s style of direct-impingement piston hybrids tended to be a little finicky when used with short barrels. It took some time to find the right combination of gas system, and gas port to create reliable short-barreled rifles. 

Additionally, these guns are gassy when suppressed. Suppressors help increase back pressure and that back pressure comes out of the rear of the gun and directly into the user’s eyes which is uncomfortable. These guns also run hot and dirty when fired in automatic mode. You could address these issues on the AR-15 platform, but it took work and effort.

And that’s where the AR-18 came in. Its short-stroke gas-piston system functions well with short barrels, and produces very significantly less gas blowback. It’s also cleaner and cooler so it functions well in full automatic. 

Several modern service rifles have been influenced by the AR-18. 

Related: Why did Colt produce the M5 family of rifles?

FN F2000 

The FN F2000 departs quite a bit from the AR-18 by assuming a bullpup format. The F2000 series maintains the short-stroke gas piston design, but places the action behind the trigger to create an extremely short rifle. The FN F2000 is a modern 5.56 caliber rifle designed to function with modern optics, accessories, and even grenade launchers. 

Its notable include the Ukrainian military, Pakistan’s Special Service Wing, the Slovenian Army, and the Special Forces Group of the Belgian Armed Forces Land Component. 

FN SCAR 

The FN SCAR, or SOF Combat Assault Rifle is the gun that will always be the SOCOM gun to me, even if it never met SOCOM’s goals. The Mk 16 and Mk 17 series offered military forces a 5.56 and 7.62 option with a variety of calibers following. The SCAR system fielded the short stroke gas piston design under a monolith receiver with ambidextrous controls, varying barrel lengths, and rails to accommodate every accessory under the sun. 

Its notable users include SOCOM, the Belgian Armed Forces, the Finnish Jaegers, the French Army, and Germany’s GSG 9 police tactical unit.

Related: The adaptable Steyr AUG – Service rifles from around the world

HK 416

The HK 416 is the most successful of the AR-18’s descendants. The 416 blends the AR-18’s gas system with the M4’s layout to create a rifle that makes everyone happy. The HK 416 comes in numerous sizes and calibers, including the HK 417, which is a 7.62 variant. The USMC adopted the weapon as an Infantry Automatic Rifle, and it’s also a favorite of special operations unis around the world. It’s known for its ergonomics, accuracy, reliability, and capability. 

Its notable users include SOCOM, the Marine Corps, German army, Ireland’s Army Ranger Wing, and Japan’s Special Forces Group. 

CZ-805 Bren 

The CZ-805 Bren series is inspired by the AR-18 and the FN SCAR series. The Bren and SCAR are very similar firearm and both come in multiple calibers. The Bren series is currently in its third generation and represents a modern, modular short-stroke gas-piston gun. It’s been quite successful for CZ and has been adopted worldwide. 

Its notable users include the Czech Military, Ukraine’s Foreign Legion, the Hungarian Defence Forces, and the French Gendarmerie’s elite GIGN unit.

SIG MCX Family 

The SIG MCX series takes cues from the HK 416 by combining elements of the AR-18 with the AR-15 series. It gives the user AR-like controls with the benefits of a short-stroke gas-piston system. The MCX is a huge family of guns – the U.S. has adopted the MCX Spear as the M7, and special operations forces have adopted the MCX as the LVAW, the SURG, and Rattler PDW system. 

Its notable users are the U.S. Army, SOCOM, Netherlands’ Maritime Special Operations Forces, the Spanish Navy, and Ukraine’s SBU Alpha Group

The AR-18 inspired many more rifles including the Howa Type 20, the FB MSBS Grot, the HK 433, and the Beretta AR160X series rifles.

The AR-18 continues to provide inspiration for a wide variety of guns, and it seems as if most modern rifles will be taking cues from the AR-18 rather than the AR or AK series.

Feature Image: A GRUFE (Special Forces Group of the Peruvian Air Force) Special Operations Defense member takes aim at a target with a FN SCAR-H rifle from a FAP Bell 412 helicopter during a helo-borne sniper training mission in support of Resolute Sentinel 2024 at Punta Lobos Air Base, Peru, June 5, 2024. . (U.S. Air Force photo by Staff Sgt. Taylor Crul)

Read more from Sandboxx News

• Upgrades ahead across the special operations helicopter fleet
• Combat swimmer operations and their importance in a near-peer conflict
• These are the US aircraft qualified to carry nuclear weapons
• Soldier skills and fieldcraft still matter despite tech advances, as Army’s newest optic shows
• Beware of the fog of war in the India-Pakistan conflict