This is a wildcat based on the .308 Winchester case necked up to accept .375 diameter bullets. John Dougherty of San Pablo, California has developed such a round and calls it the .375-08 Jaguar.
To quote John, "...The Jaguar allows one to load bullets from 200 to 300 grains in spitzer,round,flat and semi-spitzer designs and the handloader has a bullet selection that rivals any .30 caliber. The case proved to burn powder very proficiently and a 225 grain spitzer will do 2500 fps out of a 24" barrel. The 300 grain roundnose will do almost 2000fps. So what we have is .444 Marlin punch with a point blank range of 220 yards..."