The MCX Spear in .277 SIG Fury is the civilian chambering that matches the military XM5 cartridge — a hybrid brass/steel cartridge case capable of generating chamber pressures 80,000 PSI, far exceeding SAAMI standards for conventional rifle cartridges. The .277 Fury achieves 3,000 fps with a 135-grain bullet from a 16-inch barrel, penetrating Level III body armor. The civilian version uses SIG's titanium-lined hybrid case for safety compliance. Type: Rifle Action: Semi-Automatic Caliber: .277 SIG Fury Capacity: 20 Year introduced: 2022, USA Weight: 9.1 oz Overall length: 35" Status: Active Military use: Yes Intended use: military, hunting