Colt M4 / SIG MCX-Spear (XM7) / SIG XM250 (NGSW)

M4 has been the US Army's standard carbine since the 1990s — 5.56 mm, gas impingement, 14.5" barrel, M16 derivative. XM7 (SIG MCX-Spear) won the NGSW tender in 2022: a 6.8×51 mm Common Cartridge (Sig Fury) assault rifle with short-stroke gas piston. The larger round provides better penetration of modern body armor at long range and more lethality. XM250 (SIG MG-338 derivative) is the matching squad automatic weapon. SIG Sauer XM157 is a Vortex-Spitfire optic suite with laser rangefinder, ballistic computer, and "automatic aim correction" between shots.