.277 Fury: The Army’s Newest Cartridge’s Background And Ballistics

A closer look at the development, adoption and ballistics of .277 Fury, the U.S. Army’s newest cartridge.

The .277 Fury is a beast of a cartridge designed to shoot flatter and transfer more energy to its target at farther distances. The U.S. Army calls the round “next generation,” and based on .277 Fury’s capabilities, that is not an exaggeration.

Compared to the current-issue service cartridges it’s slated to replace like 5.56x45mm and 7.62x51mm, the .277 Fury offers greater energy, improved terminal ballistics and higher ballistic coefficient bullets that slip through the air with ease. It appears that America has settled on a new battle rifle cartridge to arm its troops, but just how much better is it?

Why was the .277 Fury Developed?

The U.S. Military is always looking for an edge. In 2017, the Next Generation Squad Weapon (NGSW) program was launched by the U.S. Army with the goal of replacing the M4 carbine and M249 SAW light machine gun, both chambered in 5.56 NATO, as well as the M240 machine gun in 7.62 NATO. These have served the military well—the 5.56 since 1963 and the 7.62 from way back in 1954. But warfare changes. The cartridges that our military currently uses are effective, but the 5.56, for example, has had known penetration issues in combat. Body armor has evolved to be lighter and tougher, and that means rifle cartridges need to evolve in tandem.

For the new cartridge of the NGSW program, the Army specified that it wanted a 6.8mm or .277-caliber bullet. This has been a long-time desire and has resulted in aborted attempts at the caliber, such as the 6.8mm Remington SPC. For its latest effort, the Army had its own .277-caliber bullets designed by Picatinny Arsenal weighing 130 and 140 grains with velocity potentials of more than 3,100 feet per second. 

Furthermore, firearms manufacturers were invited by the Army to submit cartridge and rifle designs for review, essentially integrated systems. For the rifle, the specifications dictated it could not be longer than 35 inches and could only weigh up to 12 pounds with accessories and optics. The weapon-cartridge system also needed to penetrate body armor out to 500 meters, hit targets out to 610 meters, and suppress targets out to 1,200 meters.

SIG's entry to the program was the 6.8×51mm Common Cartridge chambered in its XM5 rifle and XM250 LMG. SIG’s new cartridge has a maximum overall length of 2.83 inches, which means it will load and feed from any 7.62 NATO (.308 Winchester) detachable box magazine. Other submissions to the program included manufacturers such as General Dynamics and Textron Systems. 

In 2020, SAAMI, the organization that creates standards for ammunition, approved the round as the .277 SIG Fury, which sounds a helluva lot sexier than 6.8×51mm. In 2022, the Army adopted the round alongside SIG’s rifle and LMG. Uncle Sam now not only has a new cartridge, but a couple of new guns to shoot it with.

Speed + Energy = Fury 

So, why would the Army want a new 6.8mm cartridge? It already had 7.62, which is battle-proven, as well as 6.5 Creedmoor which is loved by long-range competitive shooters. The answer? The .277 has superior velocity and energy.

However, there was a tradeoff in this arms race, particularly relating to chamber pressure.

To achieve the Army’s desired ballistic properties, the chamber pressure of .277 Fury is a mind-blowing 80,000 PSI. By comparison, 5.56 NATO produces about 60,000 PSI and 7.62 NATO about 62,000 PSI. Other calibers used by the military don’t even come close to the pressure generated by the .277 Fury. The massive .50 BMG only produces about 53,000 PSI, and the .338 Lapua Magnum about 61,000 PSI. The 80,000 PSI generated by .277 Fury is a lot of pressure to contain in a cartridge case, and it’s why not just any rifle can handle it.

Case Study: .277 Fury

The extremely high chamber pressure of .277 Fury forced SIG to rethink traditional cartridge case design. Because brass alone is not enough to contain it, the company took the hybrid approach and designed a casing made of multiple types of metal.

To reinforce the .277 Fury, it uses a stainless steel base attached to a brass body via an aluminum locking washer. The base is much more robust and is strong enough to withstand the high pressure that would literally blow apart a traditional brass cartridge case. 

Though, the Fury thankfully isn’t pigeonholed to this radical case design. The cartridge can be downloaded to 65,000 PSI which allows it to safely use conventional brass cases. But this raises the question, what is the benefit of a chamber pressure at 80,000 PSI with a 135-grain bullet traveling at 3,000 fps? 

Quite simply, a flatter trajectory and more energy down range.

.277 Fury Ballistics

Compare the ballistics of .277 Fury to other military calibers like the 5.56 and 7.62 NATO and you soon see that the Fury has a distinct edge. When you pit the trajectory of .277 Fury against that of 5.56, 7.62, and 6.5 Creedmoor, you see that some bullets fall like stones. 

According to SIG, the .277 Fury loaded with a 150-grain bullet has a muzzle velocity of 3,120 fps out of a 24-inch barrel.  Compared to other currently used military cartridges, this is impressive. The common 149-grain M80 load of 7.62 from Lake City has an advertised muzzle velocity of 2,790 fps when fired from a 22-inch barrel. The 62-grain M855 load of 5.56 can achieve a muzzle velocity of 3,110 fps when fired from a 20-inch barrel, and 143-grain Hornady ELD-X 6.5 Creedmoor has an advertised muzzle velocity of 2,700 fps out of a 24-inch barrel. While that may not seem like that big of a difference for some of these, the trajectory table should speak for itself.

At 1,000 yards, the .277 Fury drops only 253.6 inches. On the other hand, the 6.5 Creedmoor drops about 306 inches, 5.56 NATO drops 421 inches and the 7.62 NATO drops 354 inches. Data doesn’t lie, and the Fury shoots much flatter than these other service cartridges. Comparably, it also delivers a beastly amount of energy. 

There is a 33-percent difference in muzzle energy between the .277 Fury and the 6.5 Creedmoor, a 23-percent difference between it and the 7.62 NATO and a whopping 83.5-percent difference between the cartridge and the 5.56 NATO. Why is this important? Kinetic energy helps to better understand the cartridge’s terminal ballistics, particularly its potential to penetrate a target.

Fast and Fury-ous Ammo Options

Since the .277 Fury is so new, only SIG is currently producing commercially available ammo. SIG’s offerings include a long-ran

ge target load and two hunting loads. While two of these cartridges produce pressures low enough to be used with traditional brass casings, one of the hunting loads is juiced up enough to require the new hybrid case design. Note that while all these loads are expensive, they can typically be found for less than the listed MSRPs.

ELITE BALL FMJ 277 SIG FURY

This is the target load, and it uses a 135-grain FMJ bullet with a 0.475 BC. Factory data states that muzzle velocity from a 16-inch barrel is 2,750 fps and 3,000 fps from a 24-inch barrel. This round is specifically designed for long-range shooting. Expect to pay about $1.70 per round for this option, as 20-round boxes have an MSRP of about $34. 

277 SIG FURY, 130gr, VENARI SOFT POINT HUNTING

If you want to put meat on the table, SIG’s traditional 130-grain soft-point option offers an advertised muzzle velocity of 2,710 fps and muzzle energy of 2,120 foot-pounds. This round is designed for whitetail deer up to elk. With an MSRP of about $42 per 20-round box, each trigger pull will cost about $2.10.

ELITE BONDED POLYMER TIPPED 277 SIG FURY HYBRID

The hybrid cartridge load uses a 150-grain polymer-tipped, boat-tail Nosler Accubond bullet that offers military-grade horsepower for the hunt. Utilizing the stainless-steel base hybrid case, the round cranks out 3,120 fps muzzle velocity from a 24-inch barrel and produces around 3,243 foot-pounds of muzzle energy. This performance isn’t cheap since 20-round boxes have an MSRP of about $80, resulting in a cost of about $4 per shot.

.277 Fury Rifles

When the .277 Fury was introduced to the shooting public in 2019, the only rifle chambered in the caliber was the SIG Cross, a lightweight minimalist bolt-action hunting rifle that weighs 6.5 pounds naked without a scope. 

SIG has since offered the MCX-Spear chambered in the cartridge as well, the company’s civilian version of the U.S. Army’s XM7 rifle. The semi-automatic rifle has similar features as an AR-15/AR-10 platform, but it uses a short-stroke piston in lieu of the direct gas impingement system found in typical ARs. Either of these rifles would do good work as a long-distance target rifle, but if I had my choice, I’d choose the lightweight bolt action, especially for hunting in rough terrain. 

At present, no other rifle manufacturers are producing guns chambered in .277 Fury. Part of the reason could be gunmakers are waiting to see if the caliber catches on with the public. Another reason could be the nature of the cartridge itself. 

Making a .277 Fury rifle is not just a simple matter of swapping barrels in an action. The pressure generated by the round means a trip back to the drawing board to beef up receiver designs or completely rework a gun. That’s a significant expense for a cartridge that is yet to prove its mainstream appeal. For companies that aren’t SIG, wait-and-see just might be the best strategy.

Niche Cartridge?

Does the introduction of the .277 Fury mean that 5.56 and 7.62 are going to be shelved? Hardly. The military will continue to use both for a long time as they work on integrating the new weapons and ammunition, and civilian shooters are too invested at this point to give either cartridge up. The future of .277 Fury with the civilian population will likely continue to increase as well, particularly if more ammunition manufacturers load the round and more rifles are chambered for it.

The Fury has both long-range competition shooting and hunting applications, but both areas have numerous rivals when it comes to performance and availability. However, the edge the .277 Fury has is huge—U.S. Military approval and backing. Nearly every caliber used by the military eventually becomes popular with civilians, and with time, this may prove true for the .277 Fury, too. 

Editor's Note: This article has been updated to more precisely express the percentage difference of muzzle energy between cartridges.

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