[4] In January 2019, the United States military began the Next Generation Squad Weapon Program to find replacements for the M4 carbine and M249 light machine gun.

[10][11] The main driving force behind the US Army's wish to upgrade its small arms came from lackluster performance when engaging insurgents abroad.

Standard caliber M4 Carbines and M249 light machine guns chambered in 5.56×45mm NATO did not have the firepower to effectively engage in long-range firefights.

[7] The SIG MCX Raptor is a short-barreled rifle variant intended to serve as a carbine, featuring an 8-inch (200 mm) barrel and a Picatinny rail tail interface for attaching either a compact buttstock or a folding PCB (pistol contour brace).

Unlike the handguard of the MCX, which slides off after pulling the front pivot pin, the MCX-MR requires the removal of two screws first.