XM5XM5 XM5 The XM5 is the US Army variant of the SIG MCX SPEAR, a 6.8×51mm, gas-operated, magazine-fed, assault rifle designed by SIG Sauer for the Next Generation Squad Weapon Program in 2022 to replace the M4 carbine. History. 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. In September 2019, SIG Sauer submitted their designs. The XM5 was designed to fire the 6.8×51mm SIG Fury cartridge in response to concerns that improvements in body armor would diminish the effectiveness  of common battlefield rounds such as the 5.56×45mm NATO (used in the M4 and M249) and 7.62×51mm NATO. On 19 April 2022, the United States Army awarded a 10-year contract to Sig Sauer to produce the XM5 rifle, along with the XM250 Automatic Rifle, to replace the M4 and M249, respectively. Operational testing of the XM5 Rifle, XM250 Automatic Rifle, XM157 Fire Control Optic platform agnostic unit and the 6.8×51mm ammunition squad weaponry is expected to begin in 2024 and does not guarantee actual widespread future issue. XM5 The XM5 is the US Army variant of