.277 Fury Ammo

Table showing at a glance the specs of a .277 Fury Ammunition.

.277 Fury: In Depth

As the long and storied service journey of the AR-15 / M16 / M4 rifle wound its way into an unthinkable seventh decade, many folks believed it would never end. Clearly, a small-arms platform that stuck around for that long was doing something right; at the very least, sixty-odd years was plenty of time to work out all the ammo, barrel, stock, and sighting system related bugs, in theory. But, not everything was just right – barrier penetration was lacking, for one. And, perhaps more importantly, the opportunity to combine several small arms cartridges – 5.56 NATO and 7.62x51mm – into one still dangled enticingly over the entire situation. Just a few years ago, with modern case, powder, and projectile tech leading the way, it seemed like a replacement could finally be found for the M4, and maybe a few other weapons, too.

In 2017, the US military launched what it called the Next Generation Squad Weapon (NGSW) program. In it, they specified a new 6.8mm caliber cartridge should be developed for use in two different rifles – one modular, mag-fed rifle, and one lightweight machine gun. As usual, multiple large firms competed against one another to develop the guns and ammo. In this case, Sig Sauer ultimately triumphed over Beretta, FN, and others when they secured a ten-year contract with the US Army in 2022. They employed a novel, brass-steel-hybrid case for their new 6.8mm ammunition, which ran interchangeably in the MCX-SPEAR and LMG 6.8 lightweight weapons platforms. Through the use of steel components near the base of the case, the Sig ammunition was able to develop an incredible 80,000-psi of chamber pressure. This is pretty remarkable for a round roughly the size of a .308 Win. Never one to miss a prime marketing opportunity, Sig named their creation .277 Fury. It drove a premium 135-gr. bullet fast –3,000/fps in fact–and performance on target was impressive.

The guns are also equally impressive. As select-fire-capable weapons designed with portability, suppression, easy barrel changes, and overall modularity in mind, they represent the bleeding edge of small arms technology–or at least the closest thing to bleeding edge that the Army can muster! These weapons are just now entering into service, so no real track record exists to speak of. And, though it was designed to replace the M4, Sig’s MCX-SPEAR won’t outnumber the older rifle on the battlefield for many years to come, if ever. Truly, odds are that M4s will serve some role or another in the armed forces for several more lifetimes. 

.277 Fury: Guns

In the US, we civilians have a long history of coveting whatever weapons our armed forces are using at the time. For all but a very few of us, owning select-fire guns is completely out of the question, so manufacturers here produce semi-auto versions of their newest creations. At present, Sig Sauer is the only manufacturer producing complete rifles chambered in .277 Fury. This isn’t a huge surprise, for several reasons. For starters, the design effort was all theirs, so their guns were ready to ship before anyone else’s. Also, due to the insane 80,000-psi chamber pressures possible in full-house loads, whatever rifle action you pit against this cartridge needs to bring the beef! Normal rifle pressures are closer to 60,000-psi, for reference. It’s likely that other manufacturers are simply approaching this round with extra caution with respect to their own firearms development efforts. That being said, Sig makes premium quality guns, so either the bolt-action CROSS or civilian model semi-auto MCX-SPEAR will make for a fantastic introduction to this cartridge, provided you can afford them. Additionally, these two guns (and this cartridge) were designed for suppressor use, and MCX-SPEAR guns are available in short-barrel configurations as well.


  • Sig CROSS - Bolt Action
  • Sig MCX-SPEAR - Semi-Auto

Why Choose .277 Fury?

If you want to sample some truly innovative cartridge technology, and you can afford one of the rifles that chambers it, then .277 Fury is where it’s at. The future of this round is unfolding before us – the Army firmed up its procurement contract with Sig just recently, in 2022 – so you have a chance to join in on the introduction as new guns and loads come out. Although rifle and ammo selection is limited for now, that won’t always be the case.

Self Defense 

  • A modular-platform rifle like Sig’s MCX-SPEAR is compact and suppressor-ready. 
  • Full performance of the ammunition can be expected from a 16” BBL.
  • Target-shooting friendly, 135-gr. lower pressure FMJ loads are available. They’re also a lot more affordable than the higher pressure loads.


  • Sig markets their bolt-action CROSS rifle as a precision hunting gun.
  • Sig also produces a 130-gr. SP round for deer hunting.

.277 Fury: Ammo Brands and Loadings

Welcome to the Sig show! Your choices for ammo–at least on the civilian market–are sold by Sig, Sig, and Sig! Luckily, there are a few different loads at present, including several that don’t cost all that much. For target shooting or plinking, grab a 135-gr. FMJ load. Or, if you’re looking to get better-than-6.5 Creedmoor performance, even when using a 16” barrel, there is a 130-gr. soft point loading for hunting deer. Both of these are loaded in a standard pressure, run-of-the-mill brass case. However, if you really want the business, the only option is the 150-gr. HPBT load featuring the unique steel and brass case construction. This load truly shows what the cartridge is capable of–just be advised that you’ll spend more than double vs. the old school brass-cased ammo. It’s a small price to pay in order to see the future of ammunition, though.

Standard Loadings

  • 135-gr. HPBT @ 3,000/fps (MIL-Only)
  • 150-gr. HPBT @ 2,850/fps

Bullet Types

  • HPBT (Hollow Point Boat Tail) - Self Defense, Hunting
  • FMJ (Full Metal Jacket) - Target
  • SP (Soft Point) - Hunting

Bullet Weights

  • 130-gr. - Hunting SP Load
  • 135-gr. - Reduced Pressure Load (Civilian)
  • 150-gr. - Hybrid Case Full Pressure Load

Velocities (16” BBL)

  • 130-gr. - 2,710/fps
  • 135-gr. - 2,750/fps
  • 150-gr. - 2,850/fps

.277 Fury: Frequently Asked Questions

No, .277 Fury is a civilian cartridge, too.
In fact, the military’s version is more accurately known as 6.8x51mm, or 6.8 Common Cartridge.

Yes. Not only does Sig sell a 130-gr. SP load for deer hunting, but they also market their larger 150-gr. full-house load as a hunting option. These two bullet weights put it in the same general area as a light 6.5 Creedmoor load, but with a lot more energy within 500-yds (especially with the 150-gr. load).

While there is no clear advantage to .277 Fury for HD vs. 5.56 NATO or .223 Remington, it will certainly work!
The MCX-SPEAR is highly reliable, compact, and suppressor ready.