If you are in a hurry and need a 6.8 I just got notice that Midway has new 6.8 uppers in stock and should ship today. (I'm not buying as I already have an Xtreme plus the Xtreme test model).
DPMS AR-15 AP4 Flattop Upper Assembly 6.8mm Remington SPC 1 in 11" Twist 16" Barrel Chrome Moly Matte with GlacierGuard Handguard, Front Sight, Flash Hider, Pre-Ban
This drop-in upper will attach to virtually any standard AR-15 lower assembly. Comes complete with charging handle, bolt and bolt carrier assembly, it is ready to pin to a complete lower assembly without modification. The AP4 upper is an A3 Flattop with a light contour barrel. This upper features GlacierGuard handguards which are an AP4 style handguard that utilize 15 internal fins, rather than the standard aluminum double-shield, for heat dispersion. These unique fins, while dispersing the heat generated by rifle fire, also provide unsurpassed strength and rigidity for the handguard. Externally, the AP4 "GlacierGuards?" feature 15 ribs that mirror the internal fins, and provide the shooter an enhanced grip.
DPMS AR-15 AP4 Flattop Upper Assembly 6.8mm Remington SPC 1 in 11" Twist 16" Barrel Chrome Moly Matte with GlacierGuard Handguard, Front Sight, Flash Hider, Pre-Ban
This drop-in upper will attach to virtually any standard AR-15 lower assembly. Comes complete with charging handle, bolt and bolt carrier assembly, it is ready to pin to a complete lower assembly without modification. The AP4 upper is an A3 Flattop with a light contour barrel. This upper features GlacierGuard handguards which are an AP4 style handguard that utilize 15 internal fins, rather than the standard aluminum double-shield, for heat dispersion. These unique fins, while dispersing the heat generated by rifle fire, also provide unsurpassed strength and rigidity for the handguard. Externally, the AP4 "GlacierGuards?" feature 15 ribs that mirror the internal fins, and provide the shooter an enhanced grip.