Sharps Bros, the manufacturer of Warthog, Hellbreaker, Overthrow and The Jack lower receivers, has introduced a new AR-15 upper receiver. It is specifically made to perfectly match the mentioned lower receivers although it will also be compatible with any mil-spec one.
The Sharp Bros upper receiver is machined out of a billet 7075-T6 aluminum with a hard coat anodized finish. The manufacturer also states that there is an additional lubricity coating inside the receiver. This upper receiver has no dust cover and no provision to install one. It comes with a forward assist assembly installed.
According to the company, this upper receiver is compatible with .223 Remington (5.56x45m NATO), .300 Blackout and 6.5mm Grendel cartridges. It will not work with large case diameter cartridges such as the .450 Bushmaster, .458 SOCOM or .50 Beowulf due to the ejection port size being not large enough. I assume, that if it fits the 6.5mm Grendel, then it should also fit the 6.8mm Remington SPC because the latter has a smaller case body diameter. In general, it should fit any cartridge with the base diameter equal or smaller than that of 6.5mm Grendel.
The Sharps Bros Billet Upper Receiver is available through their website at an MSRP of $239.95.
I think most of the people who build rifles using one of the Sharps Bros lower receivers mentioned in the first paragraph are mainly or at least partially pursuing a “cool look” goal. If this assumption is true, then probably this new upper receiver is the best choice to use in such a build.
Below are images of this upper receiver matched with the Hellbreaker, Warthog and The Jack lower receivers.