TFB First Look: SIG Sauer’s Next Generation Squad Weapons

    SIG 6.8mm SPEAR (Matthew Moss/TFB)

    As we have recently reported the US Army’s Next Generation Squad Weapons program has moved into its next phase, with three companies downselected, one of these was SIG Sauer, who had their NGSW prototypes on display at this year’s 2019 Defence & Security Equipment International (DSEI) exposition in London. TFB were on-hand to get our first detailed look at the new family of weapons.

    The MG-338

    SIG Sauer’s new MG-338 (Matthew Moss/TFB)

    The development of the MG-338 began three years ago when a Request For Proposals for a lightweight medium machine gun was posted by US SOCOM and the USMC. The SIG Sauer MG-338, designed by David Steinke, is a response to that RFP. Chambered in .338 Norma Magnum (and also 7.62x51mm), the MG-338 was previously known as the SLMAG. It is a man-portable weapon, weighing under 20lbs. It uses a short stroke gas piston system and has a recoil mitigation system with a free-floating barrel and action. SIG Sauer have not explained this system in any detail yet but did mention it also has an internal buffer in the rear of the receiver. The result of this is radically reduced felt recoil, with SIG claiming it to be within 1lb of that of an M4 Carbine. It fires from an open bolt and has a switchable feed tray which can quickly be swapped by an armourer. It has fixed headspace and timing and strips rounds from the belt on its forward stroke. It has a quick change barrel and ambidextrous controls, which ape the M4, listed as 3ft.lbs. The operator can also switch which side they prefer the folding charging handle to be on.

    The MG-338’s ambidextrous release for the ‘starter belt’ (Matthew Moss/TFB)

    The MG-338 feeds from what SIG call ‘starter belts’ which come in 30, 50 or 100 round configurations, these belt holders have a plastic lug which interfaces with a housing in the receiver – much like a conventional box magazine and well – this allows the starter belts to be quickly attached and detached from the weapon.

    The MG-338 has a 12 o’clock pic rail, here we can see the RK2000 fire control unit fitted (Matthew Moss/TFB)

    The receiver is made from aluminium with steel reinforcements in areas where wear may occur, it has a hard coat anodised finish and a 24in manganese phosphate barrel. It has two gas settings, suppressed and unsuppressed and can run one of SIG’s new next generation suppressors which minimise gas back flow. It has a side folding stock which when collapsed gives a 50in length. The Gen2 MG-338 is a matter of weeks away with some parts changes and a new forend to give a longer 12 o’clock rail for accessory mounting.

    338 NOR MAG loaded into one of the MG-338’s belts with a spoon-like tab (Matthew Moss/TFB)


    SIG’s MG-6.8 (Matthew Moss/TFB)

    While the MG-338 isn’t part of SIG’s NGSW submission it is part of the new family of weapons and is also the weapon system from which the MG-6.8 evolved. The MG-6.8 can be chambered in both SIG’s 6.8x51mm Hybrid and 7.62x51mm, requiring only a barrel change and no change to the bolt. The MG-6.8 takes the MG-338’s technology and compresses it into a package the size of an M249.

    Close up of the feed tray and ‘starter belt'(Matthew Moss/TFB)

    Right side of the weapon, note the ‘starter belt’ (Matthew Moss/TFB)

    It weighs around 12lbs and some weight saving measures have been taken to achieve this with the carrying handle removed and the MG-6.8 does not have the ability to change its feed direction. Additionally, the quick-change barrel feature is not present but is still able to change barrels if needed. Seen here in a black hard coat anodised finish it is also available in FDE. Like its bigger brother, it has an aluminium receiver but has a hammer forged steel, 16in barrel, also with a manganese phosphate finish. The weapon uses the same ‘starter belt’ system and this weapon on display has a less ergonomic release system, which is going to be replaced with an ambidextrous system more like that seen on the MG-338 above.

    Close up of the MG-6.8’s charging handle (Matthew Moss/TFB)

    It uses the same shot-stroke gas piston system and also has a similar recoil mitigation system and internal buffer which reportedly brings down its felt recoil to that of an M4 Carbine – 2ft.lbs. It has a side folding stock and a collapsed length of 37in. It can be mounted with the RK2000 fire control unit or a Romeo BT on its full-length 12 o’clock pic rail, it also had an M-LOK forend. It has two gas settings, like all these weapons, suppressed and unsuppressed. SIG describe it as “optimised for high-pressure high-velocity ammunition. The weapon can mount the new MIL-SLX68-QD suppressor.

    The SIG 6.8x51mm Hybrid ammunition with brass body and a steel base (Matthew Moss/TFB)


    The new SLX-SPEAR, has since been renamed the MCX SPEAR (Matthew Moss/TFB)

    It can now be confirmed that SIG’s NGSW-R prototype is called the ‘Spear’, feeding from a box magazine, which was not on display at the show, it fires the same 6.8x51mm Hybrid round. It is the latest evolution of the popular SIG MCX platform but with some improvements including a newly designed forend with a full-length top pic rail – though not monolithic. It has a standard AR-style charging handle but also an additional folding charging handle on the left side of the receiver – which does not remain deployed once you release it – unlike the machine guns. The side charging handle was not an NGSW requirement but a SIG design choice. In the configuration shown at DSEI the rifle has a 13in barrel and an overall length of just over 30in.

    Right side of the weapon (Matthew Moss/TFB)

    Close up of the receiver (Matthew Moss/TFB)

    The adjustable gas system with positions for suppressed and unsuppressed (Matthew Moss/TFB)

    A close up of the suppressor (Matthew Moss/TFB)

    Note the metal insert in the brass deflector – one of a number of parts that can be replaced if they wear (Matthew Moss/TFB)

    The weapon can mount the new MIL-SLX68-QD suppressor and also has an easily changeable barrel to allow the weapon to be chambered in 7.62x51mm. The one departure from standard AR/M16 controls is the bolt hold open on the right side, a small tab just above the trigger.

    Finally, here’s a look at SIG’s new hybrid case ammunition range, including 6.5, 6.8 and 7.62 offerings, which SIG confirmed will be commercially available in the future. The diagram gives us some idea of how the steel base and brass case are mated.

    SIG’s hybrid ammo range (Matthew Moss/TFB)

    I also got some quick and dirty video of the guns and put together a short video, check it out below:

    Matthew Moss

    Matthew Moss – Assistant Editor.

    Matt is a British historian specialising in small arms development and military history. He has written for a variety of publications in both the US and UK he also runs, a blog that explores the history, development and use of firearms. Matt is also co-founder of, a new video series on historically significant small arms.

    Reach Matt at: [email protected]