Royal Navy buys MCX from SIG Sauer

The Royal Navy has ordered more than 1,500 of the MCX assault rifles from SIG Sauer under Project HAY. The rifles will equip the Commando Forces operating with the Royal Navy’s Littoral Response Groups according to an 8th March announcement from the Royal Navy. 

The £6 million order will replace the C8 rifled provided by Colt Canada and be deployed alongside the Knights Armament Stoner 1 (KS-1) rifle, which was procured in September 2023 under Project Comacchio. 

The deal was facilitated by the Edgar Brothers, which is the SIG Sauer partner in the UK as the company works to bring products to the country and market them. The company indicated its intent to build upon its presence in the UK during the 2024 Eurosatory, this order seems to cement that intent. 

Comacchio set out to replace the SA80 assault rifle, which was the primary weapon of the Royal Marines, whereas Project Hay replaces the C8 in specialist roles. The KS-1 is also used by the British Army’s Ranger regiment.  

These roles include the maritime special operations-capable unit, which conducts ship interdictions and close quarters engagements as well as partner training. The MCX is designed to support these roles with a shorter barrel and the ability to change calibres between 5.56 and 7.62×39 mm – the calibre fired by Soviet assault rifles – if required. This reportedly will facilitate training in foreign countries where NATO calibre ammunition might be less available.

The MCX is 730 mm long with a 229 mm barrel, whereas the KS-1 is 818 mm to 869 mm long depending on barrel length. Both weapons are designed to carry suppressors and optical sights. 

The MCX was extensively tested in field conditions by the Royal Marines, according to the press release, building upon lessons learned during Project Comacchio. 

Calibre comment

SIG is also pitching for Project Grayburn, which aims to replace the SA80 across the British armed forces. The requirements remained unclear as of January 2025 with the British MoD in the concept phase. However, SIG has a range of rifles that it could offer, including the MCX and the XM7, the 6.8 mm assault rifle adopted by the US forces. Barretta is also positioning itself to enter the competition with its New Assault Rifle Platform (NARP) and the Sako M23. NARP is also chambered in 5.56 whereas the M23 can be chambered in 5.56 or 7.62 depending on user requirements. The ultimate direction chosen by the UK will likely depend on many factors, including of course the performance of the rifle, but also the potential for British production of components or the complete rifle.

By Sam Cranny-Evans, published on 14th March, 2025.