Sounds like it is a larger case than a 30-06. A trade-off between a 376 Steyr or lengthened .284 WW maybe. To get the performance they are claiming, it has to be burning a faster powder with that short barrel to get those values, but compare the shoulders on the case to a .338-06. They are almost identical, so the .375 case appears to be a larger diameter case. Its Hornady, so there may not be a parent case that is easily recognizable. Looks interesting, and I'm sure there will be wildcats from 6-375 all the way to 358-375 and others in less than a year.