Sig Sauer’s Multi-Caliber MCX Series. The central theme with the MCX is modularity. Users can quickly install different handguards, barrels and calibers (5.56mm NATO, 7.62x39mm or 300 Blackout), and stock configurations to suit their needs.

The upper is also designed to work with all mil-spec AR lower receivers. Anticipating the rigors that the MCX will go through, designers at Sig equipped it with wear-replaceable hard parts like the bolt cam path insert, feed ramp insert and charging handle latch points.