How the US Army refined its battle-tested, controversial M4 Carbine for modern combat

An Army weapons developer involved in the PIP project said “the heavier barrel is more durable and has greater capacity to maintain accuracy and zero while withstanding the heat produced by high volumes of fire. New and upgraded M4A1s will also receive ambidextrous fire control,” an Army statement said.

Refining the M4

The Army spent many years converting its fielded M4 carbines to M4A1 carbines; approximately 483,000, Army officials explained.

“Most of the enhancements resulted from soldier surveys conducted over time,” an Army official told Warrior Maven for 19FortyFive. 

Over the years, the Army has made more than 90 performance “Engineering Change Proposals” to the M4 Carbine since its introduction.

“Improvements have been made to the trigger assembly, extractor spring, recoil buffer, barrel chamber, magazine and bolt, as well as ergonomic changes to allow soldiers to tailor the system to meet their needs,” an Army statement said.

Today’s M4 is quite different “under the hood” than its predecessors and the upgraded M4A1 was further refined to provide soldiers with an even more effective and reliable weapon system, Army statements said. 

The M4A1 is also engineered to fire the emerging M885A1 Enhanced Performance Round, .556 ammunition designed with new, better penetrating, and more lethal contours to exact more damage upon enemy targets.

“The M4A1 has improvements which take advantage of the M885A1. The round is better performing and is effective against light armor,” an Army official told 19FortyFive.

Prior to the emergence of the M4A1 program, the Army had planned to acquire a new M4. Numerous tests, industry demonstrations, and requirements development exercises informed this effort, including a “shoot-off” among potential suppliers. Before its conversion into the M4A1, the M4 — a battle-tested weapon, and known for many successes — had become controversial due to combat soldier complaints, such as reports of the weapon “jamming.”

Continuous Upgrades for the M4

For many years, the Army upgraded and improved its M4, with some plans never passing the conceptual phase. All of the progress, however, has informed the Army’s current weapons. There has continued to be ongoing work to ensure the weapon is upgraded and maintained to the maximum extent. 

As many as four to five years ago, the Army did conduct a “market survey” with which to explore a host of additional upgrades to the M4A1. These previous considerations, which were performed under a program called the M4A1+ effort, were analyzed by Army developers and then shelved. Among the options explored by the Army and industry included the use of a “flash suppressor,” camouflage, removable iron sights, and a single-stage trigger, according to numerous news reports and a formal government solicitation.

The M4A1+ effort was designed to look for add-on components that will “seamlessly integrate with the current M4A1 Carbine … without negatively impacting or affecting the performance or operation of the M4A1 weapon,” a previous solicitation states. This kind of approach suggests the Army’s ongoing effort to look both in a conceptual and technological sense at ways to sustain upgrades and improvements to the weapon in coming years.