5.56×45 NATO, .300 AAC and 7.62×39 M43
980 (with 406 mm barrel)
229 or 406 (9” or 16”)
2.72 (with 406 mm barrel)
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The SIG MCX is a modular weapon, designed and manufactured by the US-based branch of the international SIG SAUER company and the ‘older’ sibling of the MPX submachine gun. It’s produced as a select-fire weapon (assault rifle) for military and police use and also available as a semi-automatic sporting carbine or rifle for civilian use.
Its modular design offers mission flexibility, permitting quick change of barrel lengths, calibers, stock options etc. From the ground up the SIG MCX rifle is designed to be optimized for use with quick-detachable or integrated sound suppressors (silencers), which is especially useful for various Special Forces.
The overall layout of the SIG MCX is made to be familiar to any M16 / Ar15 user, which means most US shooters and many more in other countries. Because of the proprietary modular design, most major parts of the SIG MCX (upper receiver, bolt group, barrels, forend) do not interchange with the Ar15 platform as single parts. However, the complete MCX upper receiver (with barrel, bolt group and return springs) can be installed onto any MilSpec Ar15 or M16 receiver. In this case, SIG MCX shoulder stocks can be installed using a specially designed adapter.
The SIG MCX assault rifle and semi-automatic carbine are gas operated weapons. SIG MCX uses a short stroke gas piston and rotary bolt locking system. Barrels are quick-detachable and are available in different lengths and calibers. Barrels are held in the upper receiver by two screws, concealed under the removable handguard. Each barrel has its own gas block with short stroke gas piston and manual gas regulator.
Upper and lower receivers are made from aluminum alloy and connected by two cross-pins. The rotary bolt locks directly into the barrel extension, and rides with the relatively short bolt carrier. Dual captive return springs with two guide rods form a single unit with the bolt group. Springs are located slightly above the bolt and do not extend beyond the receiver, allowing for a fully folding or telescoping stock to be installed on the weapon.
The modular forend is made from aluminum alloy. Sighting equipment and accessories are installed using integrated top Picatinny rail plus additional bolt-on rails on the forend. Shoulder stocks are removable and are available in several styles, including the side-folding or telescoping versions, as well as so called “SIG brace”, an interesting by-product of US gun laws.
All manual controls are ambidextrous, T-shaped charging handle is of AR15 style. Rifle is fed using STANAG-compatible (M16/Ar15 type) detachable magazines. Some barrels are equipped with proprietary muzzle brake with quick-mount for SIG brand detachable sound suppressors; some barrels feature a threaded muzzle which can also accept sound suppressors, but of more permanent nature.