The M4 Carbine was created for close quarters operations due to issues of the barrel length of the M16 being too long. Due to the rifle's lighter weight, compact length, and ability to address modern combat situations that happen within close quarters, the US Marine Corps adopted it as the standard infantry rifle. The Marine Corps followed the US Army who had already adopted the rifle almost 20 years ago.
The M4 Carbine is used by the Japanese Special Forces Group as their primary weapon. The weapon can be seen used by SFG during the Hakone Incident, Skirmish at Akusho, and Bombing of the Imperial Senate.
- Although based off the design of the M16, it is a different gun and was not adopted by the Marine Corp until 2015
- The US Army adopted the weapon system in 1994