In view of the fact that for a long time, many manufacturers who provide various tactical accessories such as sights and lights for carbines did not have a sign to install the interface, USSOCOM (American Special Operations Command) began to try to formulate a set of attachment interface standards for melee carbines in September 1989, and formally put forward the plan name of SOPM in May 1992.

SOPMOD plan was put forward by special forces such as USSOCOM, naval special operations forces, air force, army and navy, and entrusted to NSWC (Naval Weapons Research Center) for research. 1In May, 1999, SOPMOD with M4A 1 carbine as the weapon platform was tested in the navy and air force. Please note that this system named SOPMOD M4 is only called SOPMOD Block 1 in the plan of NSWC.

1 The main contractor of SOPM M4 is KAC (Knight Ordnance Company). SOPM M4 is not just a carbine, but a modular assault rifle system based on M4A 1. The main modules include a RIS wood guard with four sections of M 19 13 standard guide rails, a shortened quick-release M203 Grenade launcher and its sight, a KAC quick-release (QD) muffler, a KAC standby photo door, a tactical light and an An /PEQ-2 visible/infrared laser indicator.

At the same time, there are ACOG, reflective sight and a night vision sight of Trijicon, but many soldiers have replaced the reflective sight of Trijicon with M68 CCO or EOTech holographic sight. At present, M4 SOPMOD has been equipped with several special forces, including SEALs. When SOPMOD M4 is equipped with some melee tactical accessories, it will be called CQBW M4, that is, "indoor melee weapon M4", which actually comes from the same thing.

The second generation SOPM MOD Block 2 (now named SOPM MOD) is under development, and many different manufacturers are competing for this contract, including URXⅱ Ⅱ system of KAC, SIR system of ARMS and Lewis Machine &: Tool) MRP (Single Track Platform).

Other improvement projects include enhancing the aiming ability of M203 Grenade launcher at night, improving or developing a new type of Grenade launcher (EGLM plan), expanding the general muffler (including being applied to weapons such as light machine guns), upgrading/improving existing tactical accessories, and so on. As the model gun of FN company is selected for the SCAR project, the tactical accessories of SOPM MOD II will be applied to SCAR (SCAR has confirmed that the EGLM Grenade launcher will be used).

In order to facilitate the installation of KAC's QD muffler, Sophomore M4 has an oblique cut under the flame arrester, which is also the subtle difference between Sophomore M4 and M4/M4A 1. This kind of flame arrester is called QD flame arrester.