It is built on the RCM case.
The SAUM case is a better mousetrap for short actions as it is a shorter case yet with more capacity and more popularity.
The new Hornady will be a flop, and seems like they simply wanted their "own" cartridge rather than fully supporting the 6.5 SAUM. There was no call anywhere from anyone to build a cartridge on the RCM case. Has anyone even bothered to wildcat such a critter?
Hence, both will probably languish. Foolish move on Hornady's part. They could have factory-ized the 6.5 SAUM to the fullest extent and really had themselves a monopoly.
