SIG Sauer SIGM400

Operating mechanism

The SIGM400 is a semi-automatic firearm firing from a closed bolt and uses a direct impingement gas system.^[3]

Features

The M400 is offered as either a rifle or as a pistol and is intended for law enforcement, military and civilian markets. Rifles are chambered in either 5.56×45mm NATO with 14.5-inch (37 cm), 16-inch (41 cm), 18-inch (46 cm), or 20-inch (51 cm) threaded barrels, or .300 AAC Blackout with 9-inch (23 cm) or 16-inch (41 cm) threaded barrels. There are California compliant ("featureless") models for both.^[3] The .300 AAC Blackout model is tailored specifically for efficient use with suppressors, which SIG Sauer also manufactures.^{[citation needed]}

The SIGPM400 Elite PSB pistol is chambered for 5.56×45mm NATO with an 11.5-inch (29 cm) barrel and is chambered for .300 AAC Blackout with a 9-inch (23 cm) barrel. Both use a Pistol Stabilizing Brace accessory.^{[3][needs update]}

M400 PRO

The M400 PRO is an improved version of the SIG M400 chambered in 5.56×45mm NATO. Changes include a cold-hammer forged barrel, 2-stage match trigger, free-floated M-LOK handguard, folding front sight, and an updated 6-position collapsible stock.^[4]

M400 Tread

The M400 TREAD is a budget-oriented variant of the M400 named for the Gadsden flag and its slogan "Dont Tread On Me". Chambered in 5.56×45mm NATO, it features a 16-inch hammer-forged barrel with a 1:8 twist and proprietary Taper-Lok muzzle threading, mid-length low-profile gas system, 15-inch free-floated handguard,^[5] and a Magpul SL-K adjustable stock.^[6] The pistol grip can hold AA, CR123A, or CR2032 batteries.^[5] Iron sights are not included.