Best Ammo for SIG MCX The best ammo for SIG MCX depends on the exact model and caliber. The SIG Sauer MCX is a modular firearm platform available in several configurations, including the MCX Virtus, MCX SPEAR LT, MCX Rattler, and Rattler LT. Depending on the model, factory chamberings include 5.56 NATO, .300 AAC Blackout, […]