Power, Precision, and Performance - .277 Fury Ammo Explained

The .277 Fury is making waves across both the military and civilian firearms communities, and for good reason.

Developed by SIG Sauer, the .277 Fury cartridge stands as one of the most innovative ammunition breakthroughs in recent history.

With its hybrid case design, extreme chamber pressures, and unmatched velocity, the .277 Fury represents a significant leap forward in ballistic performance.

The story of the .277 Fury ammo begins with a challenge issued by the U.S. military. Looking to replace the aging 5.56x45mm NATO round and its associated platforms, the Department of Defense launched the Next Generation Squad Weapon (NGSW) program.

The goal?

To develop a rifle and light machine gun capable of greater range, improved terminal ballistics, and enhanced armor penetration.

SIG Sauer responded with a complete package: the XM7 rifle (formerly the MCX Spear), the XM250 light machine gun, and a groundbreaking new cartridge—the .277 Fury.

At the heart of the .277 Fury's performance is its hybrid three-piece case design.

Unlike traditional brass casings, the .277 Fury uses a stainless steel base, a brass body, and a locking washer.

This revolutionary engineering allows the cartridge to withstand chamber pressures up to 80,000 psi, compared to the roughly 62,000 psi of most 5.56 or 7.62 rounds.

This extreme pressure enables the .277 Fury to fire a 135-grain projectile at velocities exceeding 3,000 feet per second, rivaling magnum cartridges but in a much more compact form factor.

The result is a round that offers longer effective range, flatter trajectory, and greater energy on target. *Learn more about Ammunition Grain in our Shooter's Glossary blog article.

The .277 Fury truly hit its stride when SIG Sauer won the U.S. Army's NGSW contract in April 2022.

This victory marked the adoption of the XM7 rifle and XM250 machine gun, both chambered in .277 Fury, as the Army's new primary small arms system.

The selection was based heavily on the cartridge's superior performance in penetrating modern body armor, engaging targets at extended distances, and offering controllability and weight efficiency.

The U.S. military views the .277 Fury as a critical asset in maintaining battlefield overmatch, especially in conflicts where adversaries possess advanced armor technologies.

When comparing the groundbreaking .277 Fury to the widely used 5.56 NATO, it's clear these two rounds serve very different purposes—each engineered with its own strengths depending on mission or application.

The 5.56x45mm NATO has been the go-to cartridge for military and civilian use for decades. It’s lightweight, affordable, and has proven itself in combat and on the range.

With low recoil and high velocity, the 5.56 is ideal for quick follow-up shots and longer engagements within 500 yards.

It’s an excellent choice for home defense, plinking, and general-purpose use—especially in the AR15 rifle platform.

Enter the .277 Fury—a completely different animal.

Developed by SIG Sauer for the U.S. Army’s Next Generation Squad Weapons (NGSW) program, the Fury is a hybrid-case cartridge that combines a stainless steel base with a brass body to handle extremely high pressures—up to 80,000 psi.

That’s nearly double the pressure of standard 5.56 ammo.

With that extra power, the .277 Fury launches a 135-grain bullet at 3,000+ fps from a 16” barrel, giving it ballistic performance more comparable to .308 Winchester or 6.5 Creedmoor, but in a lighter and more compact package.

It offers a flatter trajectory, greater retained energy at distance, and superior barrier penetration—making it ideal for military applications, long-range shooting, and even big game hunting.

Although designed with the battlefield in mind, the .277 Fury is also making its way into the civilian shooting and hunting markets.

Civilian versions of the SIG MCX Spear chambered in .277 Fury are available, offering the same blistering performance in a platform built for recreational and tactical use.

Hunters are particularly drawn to the cartridge for their long-range accuracy, high muzzle velocity, and devastating terminal ballistics.

The .277 Fury is ideal for hunting medium to large game such as elk and deer, even at extended distances where traditional calibers may struggle.

The .277 Fury is more than just a military innovation—it is a paradigm shift in how we think about ammunition.

With the successful integration into the U.S. Army's arsenal and growing interest from civilian shooters, the .277 Fury is poised to become a staple in high-performance shooting for years to come.

As more platforms adopt this cutting-edge round and manufacturers ramp up commercial availability, the .277 Fury will continue to redefine the limits of what a modern rifle cartridge can achieve.

For this and all your other caliber needs shop now at Ammunition Depot!