John Maxwell
The US military is adopting a new service cartridge and Australia will likely follow as we did twice before when the US (and NATO) moved to 7.62 then 5.56. With the latest cartridge come two additional US infantry innovations developed by SIG Sauer USA – a rifle and light machinegun (LMG) – a significant step as not for 65 years has the US military implemented a revamped ammunition and equipment system.
The cartridge is the 6.8×51 and resembles the familiar 7.62×51 (308 Winchester) necked down to 6.8mm which in civilian shooting terms is .270 calibre. The big difference is a stainless-steel base with aluminium locking washer attached to a conventional brass body which allows much higher operating pressures than an all-brass case – 80,000psi as against 62,000psi for the 7.62 – and superior ballistics driving the new standard 135-grain projectiles at 3000fps with improved long-range performance and against modern body armour.
SIG Sauer is already marketing a civilian version called the .277 Fury with warnings they should only be fired in rifles able to withstand higher pressures. The downside to high chamber pressures is potentially accelerated barrel erosion and greater stresses and wear on parts. The Australian Army has been following US developments but says no decision has been made to move from the in-service 5.56 and 7.62 cartridges, Steyr rifle and Minimi and MAG58 LMGs.
“The ADF is aware of the US Army decision to adopt the Next Generation Squad Weapon and 6.8mm calibre. No decision has been taken within the ADF,” a spokesperson told Australian Shooter. Considering the US is our closest ally whom the ADF has worked closely with in operations in Iraq, Afghanistan and elsewhere and will surely do so in future, do we really have a choice?
“Logistical commonality with the US is always a consideration when developing future capability, however this must be balanced with self-reliance,” the spokesperson said, adding the Army still felt the in-service 5.56mm remained a lethal round. “However as technology continues to improve, materials related to soldier protection and options capable of delivering more energy on to a target at greater ranges warrant exploration to ensure ADF combatants retain overmatch.”
Since Federation, Australia has fielded three military rifle cartridges and matching infantry rifles. Up to the late 1950s Australian soldiers carried the .303 SMLE but as the US, UK, NATO and many others moved to the 7.62 NATO cartridge Australia followed, taking up the L1A1 SLR. In 1963 the US favoured the 5.56 cartridge and what became known as the M16 rifle, both better suited to the escalating war in the jungles of Vietnam. Some Australian soldiers in Vietnam carried M16s though the SLR remained the primary infantry reliance. In 1977, NATO nations agreed to opt for the 5.56 round and Australia again followed, choosing the Austrian Steyr AUG rifle and Minimi LMG in 5.56 (official year of initial use was 1988 hence the F88 designation of the Steyr).
Australia also stood up 5.56 production at a new plant at Benalla, Victoria using propellant from nearby Mulwala, both run by defence company Thales which also operates the Lithgow small-arms factory. During the past decade the F88 has undergone a comprehensive refresh and is now termed the Enhanced F88 (EF88), a much-improved rifle the Army sees continuing into the 2030s. Special Forces have always preferred the M4 and never really took to the Steyr.
Army is conducting a broader refresh of all its small-arms through what’s called Lethality System Project (Land 159). Tranche 1, which includes replacing the venerable Browning handgun, is well under way while Tranche 2 will consider a replacement assault rifle in the second half of this decade. Emerging from conflicts in Iraq and Afghanistan the US concluded its small-arms performed pretty well, though with some caveats about the effectiveness of the 5.56 round. In Afghanistan, insurgents initiated many contacts at ranges beyond 300m which is outside most effective 5.56 capabilities while hardy insurgents occasionally managed to continue fighting after taking 5.56 hits, an issue likely to be magnified when confronting peer adversaries wearing modern body armour.
Over the years various steps were taken to enhance small-arms’ lethality. The 5.56 cartridge started out with a 55-grain projectile but now fires a 62-grain and where once soldiers used guns equipped with iron (open) sights, optical sights are now the norm with increased hit probability. Many armies, including Australia, added designated marksmen to small units with a soldier equipped with a 7.62 calibre rifle able to place accurate fire at longer range. But even with special loadings the 5.56 cartridge had gone about as far as it could and what was needed was more lethality than 5.56 but lighter weight than the 7.62.
In 2017 the US Army launched the Next Generation Squad Weapon (NGSW) program, considering replacements for the 5.56 and 7.62 cartridges, M4 rifle, M249 LMG (their version of the Minimi) and M240 LMG (their version of the MAG58). Since World War One military ballisticians have appreciated that calibres in the category of 6.5 to 7mm projectiles sat in a sweet spot, featuring the best combinations of projectile mass and ballistic performance. The 2017 US Small Arms Ammunition Configuration Study concluded defeat of body armour could only be achieved with heavier projectiles at higher velocities which meant higher chamber pressures and from that the US military decided the new cartridge would be in 6.8mm calibre with a 135-grain projectile as standard.
It adopted the unusual stance of providing the 6.8 projectiles and leaving it to companies competing in the NGSW program to come up with a suitable cartridge and rifles to fire them. That came down to a shortlist of three – SIG Sauer US, General Dynamics and Textron Systems – each proposing its own cartridge design and firearms. During a 27-month trial period more than 1000 soldiers along with Marines and Special Forces tried out the new equipment and in April the US military announced SIG Sauer was the winner with its M5 rifle, a derivative of its MCX and M250 belt-fed LMG, both chambered for the new 6.8×51 cartridge.
Technically both releases remain in the experimental stage and their official designations are XM5 and XM250 though final specifications may change. The first will be in soldiers’ hands by October of next year and in all the US Army plans to buy 107,000 M5 rifles and 13,000 M250 LMGs under a US$4.7 billion contract with SIG Sauer.
If you’re American and well-off you can already buy a self-loading civilian version the SIG MCX Spear for US$7999 (ammo in 6.8 is in short supply). The US military has awarded Olin Winchester, which operates the Lake City Ammunition Plant in Missouri, a US$15 million contract to design a new base for NGSW ammunition and until then SIG Sauer will supply the cartridges. The extended phase-in of the new components means existing guns and their ammunition will be around for years.
So what’s so special about these new arrivals and their ammo? The US Army has revealed few details of the round’s actual ballistics other than assurances it delivers greater energy at close and long ranges than current systems. The new cartridge is heavier than 5.56 but apparently a bit lighter than 7.62 and at 9.84lb with suppressor, an unloaded M5 is 2lb heavier than an unloaded M4. The M250 is 4lb lighter than the M249 and to put that in perspective, the M5 weighs about the same as the Legacy Australian SLR.
Both new firearms feature a number of innovations with each boasting a combined suppressor and flash hider to manage what would otherwise be ferocious muzzle blast. The M5 is gas-operated with a short-stroke piston and rotating bolt with 15.3” barrel, readily changeable to calibres such as 7.62 NATO or 6.5Creedmoor. It has controls similar to the M4 but ambidextrous, retaining the AR pattern ambidextrous cocking handle with the addition of a non-reciprocating cocking handle on the left.
To maximise hit capabilities there was a separate contest for a new optic won by US firm Vortex with the M157 Fire Control Unit (FCU), at its heart a 1-8×30 scope with first focal plane reticule. This isn’t derived from any existing Vortex optic and was developed from the ground up for the NGSW program. Many of the fine details remain classified, including weight, though Vortex says it’s lighter than a comparable optic with a mounted laser rangefinder. The FCU includes an integrated ballistics calculator for the 6.8 cartridge, laser rangefinder, IR and visible aiming lasers, digital compass and environmental sensors, presumably for temperature and maybe air pressure, along with the ability to wirelessly network with other soldiers.
Vortex says their scope passed the full array of US military durability tests and feels ease of use was a key design consideration – to range a target the soldier simply presses a button and the scope calculates holdover and windage, displaying aiming point on the reticule. The US military is looking to buy 250,000 units which means Vortex won’t be supplying the civilian market any time soon but says it will consider that down the track, though likely without some of those military-specific capabilities.