THE CARTRIDGE LIBRARY · RIFLE · 6.8×51 MM

.277 SIG FURY

The commercial cartridge connected to SIG’s 6.8×51 mm military ammunition family. Explore the Army connection, hybrid cases, and the differences between a cartridge designation and a particular load.

2A Ledger reference desk · Sources checked October 18, 2026

Published cartridge dimensions · SAAMI drawing ↗

Read the dimensions

Overall · min–max: 2.700–2.825 in
68.580–71.755 mm
Case length · max: 2.015 in
51.181 mm
Bullet maximum: 0.278 in
7.061 mm
Rim diameter · max: 0.472 in
11.989 mm

The cartridge behind the new rifle

At a glance

Cartridge family: Rifle cartridge
Bullet maximum: 0.2780 in / 7.061 mm
Case length maximum: 2.015 in / 51.181 mm
Overall length maximum: 2.825 in / 71.76 mm

The Army’s SIG-designed M7 rifle and M250 automatic rifle use the 6.8×51 mm ammunition family. SIG identifies .277 SIG FURY as its commercial counterpart. Military issue ammunition and commercial products still require their own exact identification.

Army NGSW ammunition update · April 21, 2026 ↗ · SIG official NGSW announcement ↗

Origins & evolution

Background & development

The .277 SIG FURY grew from SIG SAUER’s work on a new military rifle-and-ammunition system and appeared in the commercial CROSS rifle announcement at the end of 2019. Its distinctive hybrid-case approach combined brass with a stainless-steel case head. The commercial cartridge subsequently received its own SAAMI specification, separate from the specifications for individual military ammunition types.

The Army selected SIG’s Next Generation Squad Weapon system in April 2022, including a 6.8 mm ammunition family for the rifle and automatic rifle. In May 2025, the Army announced type classification of the M7 and M250. Those milestones establish the military connection the FURY name often brings to mind. They do not make every commercial .277 FURY load identical to a military 6.8×51 mm loading: projectile, case construction and performance belong to the particular product or military designation. Its history is best understood as a linked weapon-and-ammunition development program with distinct commercial and service branches.

Unlike .357 SIG, this is a rifle cartridge. It is also separate from 6.8 SPC and .270 Winchester; a shared caliber number does not identify the complete case.

Historical sources: SIG SAUER: early CROSS and FURY commercial announcement ↗ · American Rifleman: December 2019 CROSS announcement ↗ · SAAMI: .277 SIG FURY standardization ↗ · U.S. Army: April 2022 NGSW contract award ↗ · U.S. Army: May 2025 M7 and M250 type classification ↗

Case construction matters

Military and commercial variations

Military 6.8×51 mm

The Army identifies a family of 6.8 mm ammunition for NGSW. A family designation does not specify one projectile or one ballistic record.

Commercial hybrid case

SIG describes a brass-and-stainless-steel case, designed for higher-pressure loading and short-barrel performance.

150 gr AccuBond example

SIG’s cited catalog lists H277SFAB150-20 with a Nosler AccuBond projectile. This commercial hunting example is not a military issue load.

The hybrid case concerns the cartridge case, while AccuBond describes the projectile. Keep those concepts separate when comparing products. Published military descriptions, commercial catalog specifications, and velocities measured in a particular rifle should retain their original labels.

SIG official catalog: hybrid construction and 150-grain commercial example ↗

Keep the source attached

Ballistics & barrel-length evidence

The linked primary sources establish the cartridge family and commercial construction example. They do not supply a comparable, load-specific multi-length velocity series for this guide. A barrel-length curve is therefore not plotted here.

A useful future overlay needs an exact load, recorded velocities, barrel lengths, and a disclosed test setup. The .22 ARC guide illustrates how different-rifle measurements are kept separate from factory data. A rifle’s listed barrel length alone is not a velocity measurement.

Army M250 specifications · identifies 6.8×51 mm ↗

Direct answers

Questions about .277 SIG FURY

What is the new SIG military rifle cartridge called?

6.8×51 mm. SIG identifies .277 SIG FURY as its commercial counterpart; the exact military or commercial load still matters.

Is it .357 SIG?

No. .357 SIG is a separate handgun cartridge.

Does hybrid mean a special bullet?

Here it refers to the case’s mixed-material construction. Projectile design is a separate characteristic.

Can military figures be assigned to commercial ammunition?

No. Keep the exact ammunition and test setup with each figure, and follow the firearm and ammunition manufacturers’ requirements.

Trace the facts

Sources & methodology

Compiled by 2A Ledger from the linked standards, manufacturer publications, and identified test records. Checked October 18, 2026. Historical tests and older catalogs retain their original dates; a listing here does not establish current availability.

Diameter figures preserve the cited drawing convention. Inch–millimeter conversion uses exactly 25.4 mm per inch. Factory specifications describe the maker’s test setup; your firearm, ammunition lot, temperature, and measuring method can produce different results. This is an educational factory-ammunition reference, not a reloading manual.