The AR-15 may have emerged as the symbol of new rifles, but secretly, its lesser-known sibling, the AR-18, sowed the seeds of a revolution.
Though it never reached the status of a household name, its short-stroke gas piston system, compactness, and versatile design paved the way for many of the world’s most modern military rifles today. What was initially regarded as a commercial failure evolved into a blueprint adopted by armed forces worldwide.
Here’s a glimpse at six contemporary rifles that bear the AR-18’s DNA—and why this “forgotten” gun remains among the most enduring designs in firearms history.
6. SIG MCX Series
Consider the SIG MCX the gateway between old and new. It pairs the AR-18’s piston-driven reliability with AR-15-style ergonomics, both delivering a sense of familiarity and brutish capability.
From the MCX Spear (now the U.S. Army’s M7) to the Rattler, ultracompact member of the family, this clan is designed to adapt. Suppressor shooting? Short-barreled versions? Full-auto fire? No issue—the piston design accommodates them all with reduced gas blowback and cooler operation. It’s no surprise that op-tier units from SOCOM to Ukraine’s SBU Alpha Group have adopted it.
5. CZ-805 Bren
The Bren, made by the Czechs, inherits the AR-18’s mechanical soul, combining its gas system with a new, extremely modular platform. In its third generation, the Bren is easily switchable in calibers and configurations.
That versatility has earned it a place in militaries seeking it, such as the Czech Army, Hungary’s forces, and France’s GIGN. Under its striking exterior lies the same piston-driven ruggedness that first made the AR-18 unique.
4. HK416
If there is any rifle that best represents the AR-18’s lasting impact, it’s the HK416. By combining the AR-15’s familiar controls with the AR-18’s piston cycle, Heckler & Koch created a rifle that is reliable, accurate, and simple to maintain—even in the harshest environments. Adopted by the U.S. Marine Corps as the M27 Infantry Automatic Rifle and used by special forces around the globe, the HK416 does its best work with suppressors and short barrels—exactly as the AR-18 did.
3. FN SCAR
Adaptability is the name of the game with the FN SCAR, chambered in both 5.56 and 7.62, and capable of changing barrel lengths, stacking accessories, and still working reliably in nearly any environment. That kind of modularity is straight out of the AR-18 playbook. Its short-stroke piston keeps the gun clean and cool, and it’s a favorite among units such as SOCOM, Belgium’s military, and Germany’s GSG 9.
2. FN F2000
Adapting the AR-18’s piston mechanism and putting it into a bullpup configuration, the FN F2000 is small, futuristic, and reasonably usable.
Having the action positioned behind the trigger, it is highly maneuverable without losing barrel length. Deployed by armies in Ukraine, Slovenia, and Pakistan, the F2000 demonstrates that the AR-18’s design can be modified to even the most unusual configurations.
1. Steyr AUG
One of the first and most legendary adopters of the AR-18’s piston system, Steyr AUG established the bullpup rifle design that has become the standard of modern bullpup rifles. Direct descendants of the AR-18’s bolt carrier and gas system, it is all presented in a package that has been defending military and police units since the late 1970s. Its modularity, reliability, and unique appearance have kept it current for decades.
Why the AR-18 Still Matters
The AR-18’s short-stroke piston design was revolutionary. By not leaving hot gases in contact with the bolt, it was cleaner running, cooler running, and more reliable overall, particularly in short-barreled or suppressed applications. It permitted folding stocks and simple field stripping, which suited contemporary combat requirements.
It may not have been a commercial superstar, but the AR-18 became the “American AK”—simple to build, tough in the field, and endlessly adaptable. Look closely at nearly any modern service rifle outside the AK or AR-15 families, and you’ll find its mechanical fingerprints.
The irony? The rifle that history almost forgot has been quietly shaping the battlefield for over half a century.