SIG SAUER’s new 277 SIG FURY cartridge was originally developed for the U.S. Army’s Next Generation Squad Weapons program ,which promises to replace the M249 Squad Automatic Weapon and M4 Carbine with an entirely new system consisting of lightweight 6.8x51mm ammunition, automatic rifle and rifle. The 6.8mm round must be capable of performance similar to .270 Win Short Mag. Although the government provides a special projectile and specifications for accuracy, they left it up to industry to create a cartridge to deliver it on target.

Due to the Army’s operational requirement for this new round, it requires extremely high chamber pressure, in excess of 80,000 psi.

SIG is one of three companies competing to satisfy the Army’s NGSW requirement ,which is planned to begin fielding weapons in 2022. The other two teams are led by General Dynamics and Textron Systems, but neither of these is a firearms or ammunition manufacturer like SIG.

Instead, both had to partner with others. This situation has resulted in three completely different cartridge designs.

SIG Ammunition created a hybrid case with brass body and steel head. This ammunition is used in fairly straightforward firearms which would be familiar to any service members who has fired current issue weapons. As you can see in this photo, it is similar length and diameter of 7.62mm NATO.

General Dynamics’ partner True Velocity utilized a polymer case that can be recycled and features a much less pronounced neck design. Their polymer ammunition is fired from bullpup designs.

Textron Systems offers the most ambitious cartridge. Their Case Telescoped design features a polymer case that completely encases the projectile, which is surrounded by propellant. It resembles a rimless shotgun shell and is fired from a firearm with entirely new operating system ,which pushes the cartridge ever forward through the firing cycle.

SIG’s submission was developed by SIG Ammunition at their plant in Arkansas. Their brass case with steel head offer slighter weight when combined as well more strength in the head where you need it, and a malleable case that works very well in the firing cycle.

Initially, the case was a three-piece design and included an aluminum lock washer to hold the head and case together. Eventually, they figured out how to attach the brass and steel without the internal washer. The two pieces are made using conventional ammunition machinery. The design is 23.5% lighter than the weight of an equivalent energy cartridge (.270 WSM). This exceeds the Army’s goal of a 20% reduction.

In this photo, the .270 WSM cartridge to the left is paired with SIG’s 6.8x51mm round developed for the NGSW requirement, on the right.

What makes the introduction of this new caliber so interesting is that it is being developed specifically for a military requirement. That hasn’t happened in a long time. Instead, the military has adapted sporting cartridges. Depending on which type of ammunition the Army selected, it might not be available for civilians.

SIG already had the idea for a hybrid cartridge case in mind when the Army published its product opportunity notice to the industry in November of 2017 for a Next Generation Squad Automatic Rifle to replace the Squad Automatic Weapon. By May of 2018, SIG had developed both a cartridge and a belt-fed machine gun to fire it.

Since then, they’ve gone from an initial field of 16 competitors to the three in the current phase of this Army weapon program. SIG decided the technology is mature enough to offer commercially.

Naturally, SIG wanted to capitalize on this innovation for all of its customers. SIG CEO Ron Cohn has related to me in the past that SIG is committed to their machine gun program and will offer their developments to friendly foreign governments who want to increase their capabilities, regardless of whether the U.S. Army ultimately adopts their NGSW submission. Likewise, they’ll offer what they can to the civilian market.

To this point, Jason Imhoff, Director of Ammunition Engineering at SIG, related, “The thought of civilians not having access to a new military cartridge never even crossed my mind.”

But it’s not just as simple as deciding you’re going to introduce a new cartridge to the market. SIG had to engage with the Sporting Arms and Ammunition Manufacturers' Institute or SAAMI, as it’s popularly known.

This process began in June 2019 when they submitted documentation including drawings and proof load information to the SAAMI’s summer meeting. SAAMI meets in person twice a year to consider new calibers and tend to other business.

At least initially, it was a bit of a hard sell. Due to the round’s high chamber pressures, SIG had to work with SAAMI’s Technical Working Group to develop new certification procedures. Along the way, COVID hit and slowed the process, but in a virtual meeting earlier this summer, the Joint Technical Committee approved the Technical Data Package. Although SAAMI still hadn’t published the TDP for industry use, things are moving forward.

Initially, 277 SIG FURY will be offered with the new 150-grain Nosler AccuBond projectile. It’s a strong boattail bullet featuring a polymer tip, copper-alloy jacket with a lead-alloy core and a thick heel. They’re getting 3,000 FPS from a 16-inch barrel and an additional 30 FPS for every additional inch of barrel.

Because SIG manufactures firearms as well as ammunition, they were in a unique position to take advantage of the new cartridge by integrating it in their recently released CROSS, a bolt-action rifle intended for hunting.

From its outset, the CROSS rifle was developed using 277 SIG FURY proof loads, which feature significantly higher chamber pressures in order to prove it can handle the sustained fire of the standard cartridge.

The CROSS in 277 SIG FURY is just now hitting the shelves, and SIG also plans to release a semi-automatic version of the rifle they developed for NGSW in the future, which is called the MCX SPEAR. Eventually, other companies will produce barrels and full firearms now that the caliber has a SAAMI specification. Likewise, we’ll see new cartridges for this caliber with different projectiles and powder loads.

What’s more, SIG foresees an entire lineup of SIG FURY variants of popular calibers like 6.5 CM and .308 with increased range and delivered energy on target thanks to the greater chamber pressures made possible by their hybrid cartridge design.