Was looking at the new Sig Cross Rifle (PCR). It is offered in .308, 6.5 Creedmoor and 277 Fury. I had no idea what the 277 Fury was so I Googled it. It appears it the Sig offering for the NGSW competition. Article gives a lot of details not mentioned anywhere else.
From the article:
Currently, SIG is moving forward with civilian versions of its 6.8mm cartridge developed for the competition, the 277 SIG Fury. This cartridge utilizes a hybrid case technology made from brass and other materials. The combination is rated to handle 80,000 psi of chamber pressure. By comparison, “magnum” cartridges typically produce a maximum of 62,000 psi.
277 SIG Fury Ballistics
This added pressure will drive a 135-grain bullet from SIG’s Hybrid Match cartridge 3,000 fps from a 16-inch barrel, and produce 2,694 ft.-lbs. of energy. The 135-grain bullet has a respectable .488 G1 BC.
SIG’s 277 Fury Hybrid Hunting load features a 140-grain bullet with a .508 G1 BC, launching from a 16-inch barrel at 2,950 fps. That one produces 2,706 ft.-lbs. of muzzle energy, too.
One of the benefits of creating hybrid case technology for SIG is that the case is 20-percent lighter in weight for a loaded cartridge than a standard brass-cased cartridge. The 277 SIG Fury maintains “decreased failure rates in the most vulnerable element of the case” through its “commercialization of ‘Military Technology,’” according to company experts. The end result becomes “increased range and lethality … flatter shooting … and better performance in shorter than average barrel lengths (which) reduce the overall length and weight of the firearm.”