Rocky Gibbs was an experimenter who spawned a whole series of blown out to almost straight wall 30-06 cases. The shoulder is also moved forward so you cannot simply fire factory ammo in the Gibbs chamber to make the cases. I have a 30 Gibbs I acquired from Mysticplayer a number of years ago. Interesting design that gives about 100 - 125 fps above what a factory 30-06 will give, putting it between the 30-06 and the 300 WSM, where you would expect it to be. The Gibbs company supplied dies, reamers and other Gibbs Related stuff for this cartridge series. Regards, Eagleye.