Lot of "wrong" in this thread. Here's some facts:
1) Cartridge is the same whether you call it 6.8x51MM (military) or .277 Fury.
2) 80,000psi IS (and has been for a couple years) the SAAMI approved spec for the round.
a. This pressure requires the three piece composite case (steel case head, brass case body, and locking ring to hold them together.)
b. The all brass cased version of the ammo runs at "normal" pressures.
c. Both are because the weak point at 80,000psi is the casehead and primer pocket in brass.
3) 3,000fps is 135gr bullet (military designed projectile with penetrator) from a 16" barrel.
4) Military set a spec for barrel life of twice the "useful life" of a current M4 barrel. (Which basically means how many rounds sent downrange before the weapon will not shot 4MOA or less.) For an M4, this is ~6,000 rounds. 6.8x51 military barrels use a nitriding process instead of the M4s chrome lining (and some other changes) and have gone ~14,000 rounds before accuracy falls out of required spec. What that means for aftermarket civilian barrels in terms of useful accuracy life is anyone's guess. That said, SIG has stated that all barrels it produces for this round, including for the Cross rifle, are built to the military standard.
5) SIG has stated that the composite case is "currently not reloadable" but that "they are working on it". Issue appears to be how to resize the steel case head without possibly compromising the locking ring. When you consider 80,000psi, failure of the locking ring would be a bad thing.
FYI - All of the above is public knowledge reported by Soldier Systems Daily and others who closely follow the military.
Note: I have no affiliation with SSD or SIG. I'm just ex-Army and a gun nut who has been following this process for years.