.277 SIG Fury / 6.8x51mm AR-10 Uppers

Choosing a .277 SIG Fury / 6.8x51 Upper

.277 SIG Fury is SIG Sauer's commercial name for the 6.8x51mm cartridge, the round chosen for the U.S. Army's Next Generation Squad Weapon program. Moriarti Armaments builds complete .277 SIG Fury / 6.8x51 upper assemblies for large-frame AR-10 lowers, made in Miami. Need other large-frame calibers? Browse all AR-10 upper assemblies.

Is 6.8x51 the same as .277 SIG Fury?

Yes. 6.8x51mm is the metric name and .277 SIG Fury is the commercial name of the same cartridge.

What lower receiver is compatible with a .277 SIG Fury / 6.8x51mm upper?

A .277 SIG Fury / 6.8x51mm upper requires a compatible large-frame lower receiver rather than a standard AR-15 lower. Moriarti .277 SIG Fury uppers are designed around compatible Moriarti and DPMS/LR-308-style large-frame configurations, depending on the specific model. Because large-frame AR dimensions are not universally standardized, always verify the upper and lower receiver pattern, magazine requirements, buffer configuration, and individual product specifications before pairing components.

Can I shoot .308 Winchester in a 6.8x51 upper?

No. Only fire the cartridge marked on the barrel. A 6.8x51 upper needs .277 SIG Fury / 6.8x51 ammunition.

Which .277 SIG Fury upper should I choose?

The 16" spiral fluted upper with a slanted brake and midlength gas is the handier option. The 20" SOCOM-profile upper with rifle-length gas and a Predator brake gives more velocity at distance. Both use a 1:7 twist, a 15" M-LOK handguard and a DPMS low-profile upper receiver.

Can I use 6.8x51 military or hybrid-case ammunition?

No. Moriarti .277 Fury uppers are built for commercial SAAMI-spec brass-case .277 SIG Fury ammunition, such as SIG 150 gr factory loads. Do not use 6.8x51 military or high-pressure hybrid-case (80,000 psi) loads.