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Gun Legend: The M4 Carbine Just Might Be a ‘Mini’ M16 (Pictures)

Sgt. Jacob Harrison, a U.S. Army Reserve Soldier from the 377th Theater Sustainment Command, takes aim with his M4A1 carbine at the M4 Reflexive Fire event during the 2021 U.S. Army Reserve Best Warrior/Best Squad Competition at Fort McCoy, Wis., May 22. Approximately 80 Soldiers from across the nation travelled to Fort McCoy to compete in the annually-recurring event running May 19-28. It brings in the best Soldiers and squads from across the U.S. Army Reserve to earn the title of “Best Warrior” and “Best Squad” among their peers. Competitors are evaluated on their individual and teamwork abilities to adapt and overcome challenging scenarios and battle-focused events, which test their technical and tactical abilities under stress and extreme fatigue. (U.S. Army Reserve photo by Staff Sgt. Christopher Hernandez/Released)

With the recent selection of SIG Sauer to replace the M4 Carbine history was truly made. In fact,  the M4 Carbine, which was introduced in 1994, has served since 2010 as the primary infantry weapon for the United States Army – and since 2016 for the United States Marine Corps. The M4, a 5.56x45mm NATO, gas-operated, magazine-fed, carbine assault rifle was developed during the 1980s as a shortened version of the venerable M16A2, and it has been adopted by more than 60 countries around the world.

Even as it is facing eventual replacement, it is easy to see why the M4 Carbine has been described as one of the defining firearms of the 21st century.

Latest (and Greatest) of the M16 Carbines

It would be easy to forgive anyone for mistaking the M4 for an M16 – or even the civilian AR-15 for that matter. The weapon is just the latest of carbine variants on the proven platform. Soon after the adoption of the M16 during the Vietnam War, there were efforts to shorten the weapon for close quarters operations and the first result was the CAR-15. However, it was far from a perfect solution, which essentially just chopped the barrel down to 10 inches, which reduced its range and accuracy.

During the 1970s, the U.S. military saw little need for a carbine, but in 1982 the Pentagon requested that Colt produce a carbine of the M16A2. That resulted in the development of a new variant – the XM177E2, which was later redesignated the XM4 Carbine, a select-fire weapon that offered semi-automatic and three-round burst fire.

The choice of naming convention was notable as it was meant to be a successor to the M3, the early Cold War variant of the M1 Carbine that was produced in select-fire (like the M2 Carbine) and fitted with a mount designed to accept an infrared sight for use at night or other low-level light conditions.

Essentially a shortened, lightened M16, the M4 Carbine shares more than 80 percent parts commonality with the M16A2, but with the added benefit of a longer barrel length than the CAR-15. The M4’s 14.5-inch barrel is shorter than the 20-inch barrel of the full-size M16A2, and while that comes at a slight cost in long-range performance, it is still nearly five inches longer than the CAR-15. It offers superior performance than the past M16 carbine effort.

Since its introduction, the M4 was meant to replace the M3 .45 caliber submachine gun – aka the “Grease Gun,” and not to be confused with the aforementioned M3 Carbine – as well as selected M9 pistols and M16 rifles.

India Taliban

Spc. Yuroslav Prikhodko, a truck driver with the 82nd Airborne Division’s 1st Brigade Combat Team, fires his M4 assault rifle from an alternative firing position during a marksmanship course Sept. 14, 2011, at Fort Bragg, N.C. Prikhodko’s unit, Company G, provides logistics and sustainment for 3rd Battalion, 319th Airborne Field Artillery Regiment.

Afghanistan Policy

U.S. Marines assigned to the 22nd Marine Expeditionary Unit fire M4A1 carbines during an exercise on the flight deck aboard the Wasp-class amphibious assault ship USS Kearsarge (LHD 3) in the U.S. 5th Fleet Area of Operations, Feb. 8, 2019. Kearsarge is the flagship for the Kearsarge Amphibious Ready Group and, with the embarked 22nd MEU, is deployed to the U.S. 5th Fleet area of operations in support of naval operations to ensure maritime stability and security in the Central Region, connecting the Mediterranean and the Pacific through the western Indian Ocean and three strategic choke points. (U.S. Navy photo by Mass Communication Specialist 2nd Class Casey Moore)

What If Afghanistan

A Marine with the 22nd Marine Expeditionary Unit’s female engagement team fires an M4 carbine during an advanced course of fire on Fort Pickett, Virginia, Feb. 18. The course of fire, known as Table 3, requires Marines to pivot and move laterally while shooting at targets at known and unknown distances.

US Military Afghanistan

U.S. Army Pvt. Ryan Slade (left) fires an M240 machine gun as Spc. Cody Branam fires his M4 carbine during a situational training exercise at the Grafenwoehr Training Area in Grafenwoehr, Germany, on March 22, 2012. Both soldiers are assigned to India Company, 3rd Squadron, 2nd Cavalry Regiment. DoD photo by Gertrud Zach, U.S. Army. (Released)

U.S. Marines China

Lance Cpl. Mitchell Smith, a small arms repair technician with 1st Maintenance Battalion, Combat Logistics Regiment 15, 1st Marine Logistics Group, sights in on a barrel at the 1st Maint. Bn. Marksmanship Trainer Unit on Marine Corps Base Camp Pendleton, California, Jan. 7, 2020. The MTU holds a week-long refresher course about proper holds and techniques with the M16 and M4 service rifle before allowing Marines to re-qualify on their annual range. Smith is a native of San Jose, California. (U.S. Marine Corps photo by Lance Cpl. Alison Dostie).

M4 Carbine Firing

ATLANTIC OCEAN (July 25, 2008) Fire Controlman Seaman Rachel Hubley fires an M4 carbine from the fantail of the guided-missile cruiser USS Vella Gulf (CG 72). Vella Gulf is participating in Joint Task Force Exercise (JTFEX) 08-4 as a part of the Iwo Jima Expeditionary Strike Group. (U.S. Navy photo by Mass Communication Specialist Seaman Chad R. Erdmann/Released)

The M4 has also undergone its own updates, and that has included the M4A1, a fully automatic variant for use by special operations forces. For room-clearing operations, it was determined that full-auto was better than burst fire. It was the first version to feature a removable carry handle but also was equipped with a heavier barrel to accommodate the full-auto fire.

Even as the Next-Generation Squad Weapons could begin to be deployed to units in the next couple of years, it is likely the M4A1 will remain in use with the U.S. for years to come. It is a lasting legacy of Eugene Stoner’s excellent M16 design, just improved for another generation of warfighters.

Now a Senior Editor for 1945, Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers, and websites. He regularly writes about military hardware, and is the author of several books on military headgear including A Gallery of Military Headdress, which is available on Peter is also a Contributing Writer for Forbes.

Written By

Expert Biography: A Senior Editor for 1945, Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers, and websites with over 3,000 published pieces over a twenty-year career in journalism. He regularly writes about military hardware, firearms history, cybersecurity, and international affairs. Peter is also a Contributing Writer for Forbes. You can follow him on Twitter: @PeterSuciu.