The AR-15 is probably what most people talk about when modern rifles are mentioned; however, the AR-18, its quieter but more innovative brother, was actually changing the game without anyone noticing.

With features that included a short-stroke gas piston, compactness, and versatility, the AR-18 was the base for the development of many advanced military rifles, despite being an unpopular model. It was initially a product that failed commercially, but interestingly, it became a design that was used not only by one army but by soldiers from different parts of the globe.

The following is a glance at six rifles that bear the AR-18’s DNA, demonstrating that this “forgotten” firearm has left a legacy a lot larger than its sales numbers indicate.

6. SIG MCX Series

Consider the SIG MCX to be a middle ground between traditional design and contemporary innovation. It combines the AR-18’s piston-operated reliability with the ergonomically familiar AR-15, resulting in a platform that is comforting yet brutally capable.

From the MCX Spear—embraced by the U.S. Army as the M7—to the extreme-compact Rattler, this branch of rifles lives on flexibility. Suppressors? Short barrels? Full auto fire? No issue—the piston system accommodates them all while minimizing gas blowback and keeping the action cold. It’s little wonder that premier units ranging from SOCOM to Ukraine’s SBU Alpha Group have adopted it as their go-to gun. 

5. CZ-805 Bren

The Czech-manufactured Bren adopts the AR-18’s mechanical soul and encases it in a very modular, contemporary package. In its third iteration, the Bren is easily reconfigured for varying calibers and mission configurations.

That adaptability has earned it favor from units such as the Czech Army, Hungary’s military, and France’s GIGN. Behind its streamlined look is the same piston-driven ruggedness that made the AR-18 so lasting.

4. HK416

If there’s one rifle that most demonstrates the enduring legacy of the AR-18, it is the HK416. Heckler & Koch combined the AR-15 controls with the AR-18’s piston action to create a rifle that’s accurate, reliable, and simple to maintain—no matter the hostile conditions.

Deployed by special troops and taken up by the United States Marine Corps as the M27 Infantry Automatic Rifle, HK416 is best with suppressors and short barrels—much like the AR-18 used to be.

3. FN SCAR

Few rifles are more versatile than the FN SCAR. Available in both 5.56 and 7.62, with detachable quick-change barrels and accessory rails, it can be configured for nearly any mission. This type of modularity is directly from the AR-18’s playbook. Its piston design makes it clean and cool even when run hard, so it has earned the favor of SOCOM, the armed forces of Belgium, as well as Germany’s elite GSG 9.

2. FN F2000

The FN F2000 uses the AR-18’s piston system and puts it within a bullpup layout, creating a short, futuristic carbine that doesn’t compromise barrel length.

With the action behind the trigger, it’s extremely agile—perfect for close-quarters work. Armies in Ukraine, Slovenia, and Pakistan have all used it, demonstrating that the AR-18’s fundamental design suits alternative configurations.

1. Steyr AUG

One of the earliest and most famous users of the AR-18’s piston configuration, the Steyr AUG established the benchmark for the modern bullpup rifle. Its bolt carrier and gas system trace directly to the AR-18, packaged in a unique design that has been used by military and police units since the late 1970s.

Its modularity, reliability, and unmistakable profile have seen it serve for decades, with upgrades keeping it current to the present day.

Why the AR-18 Still Matters

When it came out, the AR-18 short-stroke piston design was prescient. By isolating hot gases from the bolt, it operated cleaner, remained cooler, and provided improved reliability—particularly in suppressed or short-barreled configurations. Its foldable stock provisions and field stripping ease made it ideally suited to contemporary combat requirements.

Though it never became a commercial hit, the AR-18 earned the nickname “the American AK” for its simplicity, toughness, and adaptability. Look beyond the AK-47 and AR-15 families, and you’ll find its engineering fingerprints on nearly every modern service rifle.

The irony? A rifle that history almost overlooked has been quietly shaping the battlefield for over fifty years.

Among so many planes to fly through World War II skies, few were as distinct as the Lockheed P-38 Lightning. Its dramatic twin-boom appearance, massed nose armament, and incredible range made it a singular and unforgettable symbol of the Allied aerial campaign—particularly in the Pacific, where its performance left so many competitors in the dust.

The Lightning saga started in 1937, when the U.S. Army Air Corps made a challenge: design a high-flying interceptor with heavy firepower and scorching climb rate. The catch? No American engine of the day would be able to muster the necessary punch.

Lockheed’s Hall Hibbard and young Clarence “Kelly” Johnson opted to double the solution—literally—by placing two turbo-supercharged Allison V-1710 engines on an innovative twin-boom airframe.

This configuration not only gave the power needed but also enabled all guns—four .50-caliber machine guns and a 20mm cannon—to be placed in the nose. With all guns firing in a straight line, pilots could hit targets at half a mile without concern about wing-mounted gun spread.

The prototype made its maiden flight in January 1939, but early models had their share of issues, including hazardous tail flutter at high speed.

Lockheed engineers continued to hone the design, adding self-sealing fuel tanks, armor plating, and aerodynamic modifications. By the time the P-38J came out, it could reach 414 mph, reach 44,000 feet, and featured things well ahead of its time—tricycle landing gear, an all-weather cockpit, and a sturdy all-metal construction.

During combat, the Lightning was an honest multi-role aircraft. It could escort bombers deep into enemy territory, attack ground targets, perform bombing missions, or reconnoiter as a spy plane. In the huge Pacific theater of operations, its range was a war winner, allowing missions over open ocean that would be out of the question for many other fighters.

Its twin turbochargers performed at high altitudes, providing U.S. pilots with the decisive advantage over Japanese planes. Though not as dominant in Europe—where agile German fighters preferred low-altitude dogfighting—it was still crucial there.

The P-38’s reputation was also cemented by its aces. America’s highest-scoring fighter pilot with 40 victories, Richard Bong, was awarded the Medal of Honor flying a Lightning. Thomas McGuire trailed closely behind with nearly that many victories.

One of the P-38’s most legendary moments occurred in April 1943, during Operation Vengeance, when a squadron of P-38s made a bold low-level intercept over the ocean to ambush Admiral Isoroku Yamamoto—the mastermind behind Pearl Harbor. The success of the mission was a psychological and strategic setback for Japan’s war effort.

On paper, the P-38 was every bit as capable as its combat history implied. 52 feet wide and almost 38 feet in length, it weighed almost 20,000 pounds fully loaded for takeoff. Combined, its two engines produced about 2,000 horsepower, rising at 2,700 feet per minute and cruising comfortably at more than 39,000 feet altitude.

There were specialized versions, such as the F-5 photo reconnaissance model that sacrificed guns for cameras, and the “droop-snoot” variant that accommodated a bombardier in the place of its nose weapons to provide precision bombing leadership.

Though fewer than 10,000 P-38s were produced—well below the P-47 Thunderbolt or P-51 Mustang—it was a large impact.

Its innovative design put its mark on flight, one that has influenced subsequent aircraft like the F-35 Lightning II, which bears not only the name, but the forward thinking of its WWII ancestor.

The P-38 Lightning is a symbol of daring imagination and combat versatility today. Either in museums, flying at airshows, or in the memories of veterans, it serves as an inspiration that great engineering can shift history—and in some cases, the most unusual aircraft become the most legendary.

Throughout the first period of the Cold War, the US had to face a big question about the way its bombers would manage to go deep into areas controlled by the enemy and protect themselves against faster enemy fighters, long-range missiles, and the general anxiety caused by the threat of nuclear war. One of the solutions to the riddle was the “penetration fighter”—a bomber’s companion, an aerial guard that would rescue the airspace from threats and then return to the base.

Lockheed’s response to this issue was the XF-90, designed at the Skunk Works legend by Kelly Johnson and Willis Hawkins.

Taking a lesson from the P-80 Shooting Star, the XF-90 was state-of-the-art in drawings: 35-degree swept wings, Fowler flaps, leading-edge slats, and a swept wings-afterburners-tip tanks combination novel to home production.

Its tail surfaces were adjustable in both directions, another innovative step forward.

But engineering superiority had its price. The XF-90’s airframe was constructed from 75ST aluminum—stronger by far than the more conventional 24ST—but also considerably heavier.

The consequence was an aircraft that would endure incredible forces, such as nuclear shock waves, but whose two Westinghouse J34 turbojets simply could not generate enough power.

Though the plane theoretically achieved 665 mph, with a range of 2,300 miles and a ceiling of 39,000 feet, it fell behind Air Force requirements and its competition.

Flight testing exposed its deficiencies. The XF-90 was able to break the sound barrier only in a dive, and even takeoff needed rocket-assisted boosters.

It was compared unfavorably with competitors such as the McDonnell XF-88 and North American YF-93, as it was slow, clumsy, and underpowered.

When the Air Force chose the XF-88 as its favored aircraft, the penetration fighter idea lost momentum as strategic needs changed and appropriations ended.

But the XF-90 became oddly famous due to its unparalleled durability. One of the prototypes was subjected to stress tests at the National Advisory Committee for Aeronautics, and the second one was shipped to the Nevada Test Site for nuclear weapons tests.

The tests yielded surprising results: a one-kiloton explosion produced minor fractures only, a 33-kiloton explosion crumpled the nose but did not suffer catastrophic structural damage, and even a 19-kiloton explosion that ripped off the tail left the plane mostly intact.

Amazingly, engineers assessed that it would only take 106 hours to return the plane to airworthiness after the initial explosion.

Years later, the radiation-stained pieces of the XF-90 were unearthed, restored, and put on exhibit at the United States Air Force National Museum in Dayton, Ohio—a rare reminder of a jet that withstood three nuclear explosions.

Though it never saw active duty and failed to fulfill its intended mission, the XF-90 influenced future designs like the F-104 Starfighter. Its story demonstrates that even “failed” aircraft can push technological boundaries and that some machines are built tough enough to endure both battlefield stress and atomic fire.