What We Know About The 6.8×51 | 277 SIG Fury [UPDATED]

Since the announcement of SIG SAUER’s victory in the Next Generation Squad Weapon program, the U.S. Army said America’s future adversaries were a major contributing factor in choosing the 6.8×51 SIG cartridge.

The Spear XM5 and the SIG Light Machine Gun (XM250) run the recently developed 6.8×51 (277 SIG FURY) hybrid steel/brass ammunition.

What We Know About The 6.8x51 | 277 SIG Fury

Before we get into the weeds of the cartridge itself, you need to understand the why behind it. The Army was not requesting a new cartridge design, just to do something new.

There is actually some sound reasoning behind their decision and that reasoning has to do with our near-peer adversaries.

Does The Military Need The New 6.8×51?

During an Army Press Briefing on the Next Generation Squad Weapon, Brigadier General Larry Q. Burris, the Army’s Soldier Lethality Cross-Functional Team Director, said their goal was to achieve a "clear, decisive, and sustainable overmatch against our near-peer adversaries."

What is a near-peer adversary? A near-peer adversary is a country with a large industrial base and military capabilities close to that of the United States. If you’re up to speed on who the military superpowers are around the world, then that statement alone should tell you who our near-peer adversaries are. And it’s not the middle east. We’re talking about China and Russia.

The reasoning for the new 6.8×51 cartridge is a result of an analysis of what our near-peer adversaries are using, so let’s quickly unpack that to give you a better understanding of the why.

What Are The Russian and Chinese Military Using?

Russia hasn’t made any significant changes to its military small arms since 1974. Consequently, its 5.45x39mm round doesn’t have any advantages over the 5.56. The 5.45×39 cartridge was Russia’s attempt to follow what other militaries were doing and produce a similar outcome with only minor changes. It did nothing to improve their small arms capability.

Red Army Standard – 5.45×39 – 60 Grain – FMJ – 1,000 Rounds

at TrueShot Gun Club
Prices accurate at time of writing

Moving to the new 6.8×51 round will put the U.S. military significantly ahead of Russian small arms in terms of effective range, energy on target, and overall lethality. Russia doesn’t have the money, especially now with the newly imposed sanctions, for a major upgrade to its military small arms program.

Additionally,  they don’t have robust private sector arms companies to lean on the way the U.S. Army does, so we’re not expecting any significant changes to their small arms any time soon.

China moved from the common 7.62x39mm round to its own proprietary 5.8x42mm round, which has a slight edge over the 5.56 round the U.S. Military is using. They have also been migrating from a bullpup design rifle to the QBZ-191 Assault Rifle. The ballistics of this new proprietary round combined with the newer rifle give China an advantage when compared to the 5.56 round.

The Chinese QBZ-191 Assault Rifle shoots a heavier bullet at greater energy than the 55-grain M193 ammunition. However, the hotter 62-grain M855 rounds close the gap and are probably of similar performance.

WINCHESTER AMMO 5.56 M855 62 FMJ Win LC 420rd Stripper Clip Green

at Kentucky Gun Co
Prices accurate at time of writing

Moving away from 5.56 to 6.8×51 is a complete game-changer. With bullet weights almost double and velocities a little better than the Chinese rounds, there’s no question about who will have battlefield superiority.

Although the 6.8×51 SIG cartridge is for the military, the civilian equivalent is the 277 SIG Fury.

What Is Different About The 6.8×51 (277 SIG Fury)

A bold move like this isn’t typically met with simple acceptance. SIG SAUER unveiled the new 277 SIG Fury cartridge in late 2019, but it didn’t receive SAAMI approval until November 2020.

With a factory-produced cartridge loaded to 80,000 psi, it was uncharted territory that wasn’t explored until now. To put that into perspective, A standard cartridge, like .308 Win, produces roughly 60,000 psi. A magnum cartridge, like .300 Remington Ultra Magnum, produces roughly 66,000 PSI. 80,000 psi is a tall order, and SIG made it happen.

The new NGSW weapon systems are chambered to shoot the new 6.8×51 SIG hybrid ammunition. Being loaded at higher pressures results in increased velocity and terminal performance.

The 277 SIG Fury and the military 6.8×51 SIG feature a conventional brass upper case body with a steel alloy bottom, and case-head section. Hence the name, hybrid ammunition, the hybrid design allows the ammo to run at significantly higher pressures than conventional ammunition.

The new 6.8×51 SIG Hybrid ammo gives the new NGSW guns significant advantages over the existing M249 SAW and M4 Carbines.

"Using patent-pending technology the SIG Sauer Ammunition Division has engineered a completely new cartridge resulting in a more compact round, with increased velocity and accuracy, while delivering a substantial reduction in the weight of the ammunition….

The SIG Sauer Lightweight Belt-Fed Machine Gun (NGSW-AR) doubles the effective range and is 40% lighter than the current M249 while maintaining the preferred belt-fed operation, with reduced felt recoil to increase accuracy. The SIG SAUER Rifle (NGSW-R) is built on the foundation of the battle-tested MCX platform with the added firepower of the 6.8×51 round." – SIG SAUER

6.8×51 Ballistics

80,000 PSI is the key to getting high velocities from a short barrel. This new cartridge does not use standard powders either. These loads are new proprietary powder blends SIG has developed while developing this round for the military.

SIG Sauer claims that the 277 SIG Fury cartridge has performance superior to the 6.5mm Creedmoor, exhibiting 6 to 9 feet less bullet drop at 1,000 yards, all while delivering 20–25% greater energy on target.

FEDERAL AMMO 6.5 Creedmoor 140Gr Gold Medal

at Kentucky Gun Co
Prices accurate at time of writing

The SIG 277 Fury Hybrid Hunting load features a 140-grain bullet with a .508 G1 BC, and a velocity of 2,950 fps when fired from a 16" barrel. Additionally, the hunting load produces 2,706 ft.-lbs. of muzzle energy.

One benefit of the SIG hybrid case technology is that the case is 20 percent lighter for a loaded cartridge than a standard brass-cased cartridge.

According to SIG Sauer, the 277 SIG Fury maintains "decreased failure rates in the most vulnerable element of the case" through its "commercialization of ‘Military Technology,’".

Comparative Analysis: .277 Fury vs 5.56 Ammunition

In the pantheon of small caliber, high velocity cartridges, two names have recently been echoing within the walls: .277 SIG Fury and 5.56x45mm NATO. The former is a newcomer in the world of ammunition, having been introduced by renowned firearm manufacturer SIG Sauer under the designation ‘sig xm5’, while the latter is a well-established workhorse that has seen decades of service in militaries around the world.

The .277 Fury represents SIG Sauer’s innovative drive to redefine performance parameters within hunting/target shooting applications and perhaps even military standards. This cartridge is designed to operate at extraordinarily high chamber pressures, enabling it to reach velocities that few other rounds can match.

On the other hand, we have the ubiquitous 5.56mm NATO round, an evolution from its precursor—the .223 Remington—that has become a stalwart due to its reliability and versatility across a plethora of shooting conditions. When comparing these two – ‘.277 sig fury vs 556’, or more pertinently ‘.277 fury vs 223’ from whence came the 5.56—the contrasts are captivatingly instructive; not just about how far technology has come, but also about how tried-and-true solutions can persist through changing times.
What We Know About The 6.8x51 | 277 SIG Fury

Calibers in Context

Whether it’s among soldiers on a military base or enthusiasts at a local shooting range—the topic invariably shifts toward ammunition; which caliber is better for what purpose? It becomes even more pertinent when we involve rounds like .277 Fury and 5.56 NATO which are both capable but distinctive in their own right.

The importance lies not just in understanding bullet diameter or muzzle velocity but knowing the potential trade-offs between speed, energy, accuracy, and recoil. A detailed comparison between ‘.277 fury vs 556’ isn’t merely an academic exercise; it’s a practical guide that aids in decision-making for battlefield strategy or hunting expeditions.

The broad acceptance of 5.56 NATO round is a testament to its performance and adaptability whereas the emergence of .277 Fury signifies the incessant pursuit of pushing the boundaries in ammunition capabilities. Thus, these two rounds embody the continual evolution that keeps firearm technology moving forward at an unceasing pace.

The Birth of .277 Fury

The .277 Fury, a groundbreaking cartridge developed by SIG Sauer, has its roots in the company’s quest for innovation and precision. This round emerged as an answer to the United States Army’s Next Generation Squad Weapon (NGSW) program call for superior firepower and lethality.

SIG Sauer brought forth the .277 Fury with a unique hybrid case technology that departs from the traditional brass casing, promising increased performance while staying within manageable recoil limits. The conception of .277 Fury involved extensive research by some of the most skilled ballistic engineers at SIG Sauer.

When it came to producing powerful yet compact ammunition suitable for both rifles and machine guns, these experts went above and beyond their usual caliber parameters. Their vision was to develop a round that could outperform existing military cartridges in terms of range and power.

In terms of objectives, one of the key drivers behind developing the .277 Fury was to create a cartridge that could deliver significantly better ballistics than anything currently available in similar size constraints. The balance between high performance and manageable recoil made this ambitious goal achievable.

The Role of SIG Sauer in Its Development

As a renowned firearms manufacturing company, SIG Sauer played an instrumental role in shaping what we now know as .277 Fury. Their dedication to pushing limits is exemplified by this new breed of ammunition which competes directly with 5.56 rounds on several factors – leading many firearm enthusiasts into discussions about 277 sig fury vs 556.

SIG’s signature XM5 rifle served as an experimental platform when developing this new ammo type — affording them invaluable feedback on how such novel cartridges interacted with established systems. This hands-on approach greatly contributed to perfecting what would become revolutionary ammunition.

SIG Sauer’s mastery over advanced material sciences further enabled them to develop hybrid case technology – a significant differentiator for the .277 Fury. By combining brass and steel in the casing, they achieved a lighter yet stronger cartridge that could withstand higher chamber pressures, resulting in increased velocity and range.

Evolution of 5.56: From .223 Remington to NATO Standardization

The 5.56x45mm NATO cartridge, better known as the 5.56, has an intriguing history dating back to its origin as the .223 Remington in the early 1960s. As these rounds became prevalent through military adoption, comparisons such as 277 Fury vs 223 became increasingly common among firearm enthusiasts.

In its initial stages of development, manufacturers aimed at producing superior ammunition that could deliver high-velocity projectiles with increased accuracy over longer ranges while managing recoil effectively — a purpose eerily similar to what drove SIG Sauer towards creating their .277 Fury.

Over time, this round saw widespread adoption and eventually became a NATO standard issue by the late 1980s — largely due to its impressive performance and reliability across a variety of situations. This decision led to its implementation by numerous military forces worldwide making it one of the most popular ammunition types today.

Widespread Use in Military and Civilian Applications

From an everyday sporting round to becoming an integral part of military operations across the globe, it’s safe to say that the 5.56x45mm cartridge has indeed come a long way since its inception. This popularity surge can be partially credited to its versatility — proving highly effective whether used in infantry rifles during combat or precision shooting sports.

In military applications, specifically within NATO countries, the usage of 5.56 is nearly ubiquitous alongside select fire rifles like M16 and M4 Carbine variants which are synonymous with this cartridge type due to their reliable performance on battlefields worldwide. Beyond military engagements though is where we often find extensive discussions revolving around topics such as 277 Fury vs 556.

The wide acceptance and compatibility of the 5.56 ammunition with civilian semi-automatic rifles has made it a popular choice amongst shooting enthusiasts, hunters, and sport shooters. Its manageable recoil, good accuracy at medium ranges, and relatively cost-effective production have contributed to its popularity in a myriad of civilian applications.

A Detailed Analysis of .277 Fury

An Examination of Bullet Diameter, Weight, Velocity, and Energy

The .277 Fury cartridge holds a central position in the discussion of 277 Fury vs 556. It features a bullet diameter of 0.277 inches that transcends the widely used .223 Remington and 5.56mm NATO bullets. The weight varies between 135-140 grains for most commercial loads, a substantial increase compared to the standard range of the 5.56.

The velocity is another pivotal factor that sets this round apart from its counterparts; it can reach up to an impressive speed of approximately 3000 feet per second, delivering a massive energy load upon impact which often ranges up to about 2650 foot-pounds (ft-lbs). These specifications elucidate why many firearm enthusiasts are curious about how the performance of the SIG XM5 would be influenced by this high-speed powerhouse.

The case design behind the .277 Fury is unique and it’s one of its major distinguishing factors in examining ‘277 sig fury vs 556’. The foundation lies within SIG Sauer’s proprietary shell case technology. This hybrid approach employs a stainless-steel base coupled with a brass body which reinforces case strength, ensuring that it can sustain high chamber pressures beyond what traditional brass cases can survive.

This hybrid case technology results in higher ballistic coefficients leading to greater accuracy at longer distances and increased velocity which has drawn comparisons between ‘277 fury vs 223’. Moreover, this design also contributes towards reducing ammunition weight—a critical consideration for military applications.

Comprehensive Review | Specifications Of The 5.56

While discussing ‘277 fury vs 556’, it’s essential to familiarise ourselves with the technical specifications of the 5.56. The bullet diameter is approximately 0.224 inches while the weight is typically between 55-77 grains, depending on the specific load.
The velocity of a standard 5.56 round varies between ranges of about 2,750 to 3,100 feet per second and can deliver an energy range from approximately 1,100 to up to about 1,300 ft-lbs. These figures might be slightly dwarfed when compared to the .277 Fury’s stats but are still significant nonetheless.

Arguably less complex than its .277 Fury counterpart, traditional brass casing is employed for manufacturing most of the commercially available ammunition including the commonly used 5.56 NATO cartridge. This means that it doesn’t share the hybrid case technology seen in the .277 Fury cartridges which has prompted many comparisons in ‘277 Fury vs 556’. While this conventional design may not offer quite as much durability or withstand as high chamber pressures as hybrid cases do, they are well proven over years of service in both civilian and military applications worldwide and remain a reliable choice for most users.

Muzzle Velocity & Energy Comparison

When the .277 SIG Fury exits the muzzle, it does so at a particularly astonishing speed. To put it in perspective, the muzzle velocity of .277 Fury can reach up to 3000 feet per second (fps), a number that trumps the average 5.56 which usually falls in the range of 2700-3200 fps. However, when delving into energy comparison, we find another striking divergence.

The .277 Fury’s muzzle energy can exceed up to 2258 foot-pounds (ft-lbs) – a colossal figure indeed when contrasted with the average 5.56’s muzzle energy that typically measures around 1300 ft-lbs. The difference becomes even more pronounced when comparing heavier loads; for instance, a heavier .277 load can generate higher velocity and subsequently generate higher energy – an asset not readily available in conventional rounds like the 5.56 or even its predecessor the .223 Remington, thus further cementing ‘277 sig fury vs 556’ and ‘.277 fury vs 223’ debates in favor of this innovative round.

Effective Range & Accuracy Comparison

In evaluating effective range and accuracy between these two rounds one cannot simply dismiss one over the other as both demonstrate impressive capabilities albeit under different circumstances.

The SIG’s .277 Fury exhibits an effective range that exceeds traditional military cartridges such as the venerable NATO standardized 5.56 and older generation rounds like .223 Remington by considerable margins.

Both rounds perform remarkably well in terms of accuracy, matching each other closely across different ranges thanks to their design and ballistic properties. However, under the same conditions, SIG’s new round slightly edges out its competitor. This advantage comes from its lower drag coefficient, which helps it maintain a more consistent, flatter trajectory over longer distances.

Military Use Scenarios for Both Rounds

When considering military use scenarios, the ‘.277 Fury vs 5.56’ debate becomes more nuanced. The 5.56, being the NATO standard round, has seen extensive battlefield use, and its effectiveness under diverse combat scenarios is well documented. However, this doesn’t mean that it doesn’t have its limitations.

Enter .277 Fury – developed to replace the venerable 5.56 in certain military applications under SIG’s next-generation squad weapon project (or the ‘SIG XM5’ project as some call it). Its superior long-range performance and higher energy are clear advantages that could potentially address some of the limitations of the current military rounds.

Civilian Use Scenarios for Both Rounds

Both cartridges serve specific purposes, thanks to their unique characteristics. The 5.56mm, with its broad availability and proven dependability, continues to be a favored option for civilians. It’s commonly used for home defense and varmint hunting because of its high velocity, reliable accuracy, and relatively low recoil.

The .277 Fury on the other hand with its higher energy levels can transcend into larger game hunting realms where conventional rounds like 5.56 would not be traditionally recommended due to ethical hunting considerations – providing hunters with a single solution for both home defense as well as big-game hunting needs thus further solidifying ‘.277 Fury vs 556’ debates in favor of this flexible round.

Potential Impact on Military Standards with the Adoption of .277 Fury

The .277 Fury’s potential to change the current military standards is significant. With its hybrid case design and superior performance, it could eventually usurp the long-standing dominion of 5.56 rounds in military applications.

When considering 277 fury vs 556, the former’s unique ability to handle pressures that are over 50,000 PSI higher than traditional brass-cased ammunition might be a game-changer in terms of increased velocity and range. In real-world warzones, this could mean greater hit probabilities and lethal effects at extended distances – a factor that may induce militaries worldwide to reconsider their caliber choices.

The recent testing by United States Special Operations Command (SOCOM) of SIG’s Next Generation Squad Weapon system – featuring .277 Fury as well as SIG’s proprietary new lightweight machinegun cartridge (the sig xm5) – strongly suggests a shift towards new ammunition technology is on the horizon. From an economic perspective, however, militaries would need to weigh benefits against trade-offs.

A switch from ubiquitous 5.56 rounds to .277 Fury would necessitate extensive changes in logistics and existing weaponry. Furthermore, costs associated with the adoption of new ammunition can be prohibitive for some nations’ budgets.

Looking Ahead

As we look towards future prospects for these two industry heavyweights—the question isn’t simply ‘277 fury vs 556?’ but rather ‘Which will adapt better to evolving needs?’. The potential future adoption of .277 Fury as a new NATO standard could significantly change geopolitical dynamics around small arms production and distribution—a profound ripple effect across global defense industries.

The ‘SIG XM5’, an advanced rifle system designed around this new cartridge, stands as a testament to SIG Sauer’s commitment to promoting .277 Fury’s wider acceptance. Meanwhile, the resurgence of interest in the 5.56 as a home defense and sport shooting round among civilians also seems poised to continue given its track record and accessibility.

Although it would be rash to predict with certainty, one can nonetheless entertain an optimistic view of these developments. A future where both cartridges not only coexist but thrive in their respective niches seems not just plausible, but eminently probable.


Now I know it sounds like we’re harping on the 5.56 round because there is a new girl in town, but keep in mind that since the 1960s the US and NATO have been using 5.56 with outstanding success.

The 5.56 round performs great out to roughly 300 yards regarding terminal ballistics. They do not suit the cartridge for barrier penetration or shooting past 300 yards. When the 5.56 cartridge was developed and the type of warfare the United States was involved in, namely the Vietnam War, the cartridge made sense. It well suited them for fighting in the confines of a dense jungle environment.

Fast forward to the GWOT and the round still performed relatively well in the urban environment, but where it showed its weakness was outside of those urban areas where you are taking shots out past 300 yards.

As warfare evolves so should the weapons and ammunition. With the battlefield developing and our near-peer adversaries becoming more of a threat, the Army decided it was time to make the move to not only a new weapons system but a superior round that outperforms anything else out there.

Related ArticleM855 vs M193 | Which One Should I Buy?

Table of Contents

  • Does The Military Need The New 6.8×51?
  • What Are The Russian and Chinese Military Using?
  • What Is Different About The 6.8×51 (277 SIG Fury)
  • 6.8×51 Ballistics
  • Comparative Analysis: .277 Fury vs 5.56 Ammunition
  • Calibers in Context
  • The Birth of .277 Fury
  • The Role of SIG Sauer in Its Development
  • Evolution of 5.56: From .223 Remington to NATO Standardization
  • Widespread Use in Military and Civilian Applications
  • A Detailed Analysis of .277 Fury
  • Comprehensive Review | Specifications Of The 5.56
  • Muzzle Velocity & Energy Comparison
  • Effective Range & Accuracy Comparison
  • Military Use Scenarios for Both Rounds
  • Civilian Use Scenarios for Both Rounds
  • Potential Impact on Military Standards with the Adoption of .277 Fury
  • Looking Ahead
  • Conclusion

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