I picked up a copy of "Gunsmithing" by Dunlap, printed in 1950, and it has drawings and brief discussion of the 300 Pheifer, which is 300 H&H with a shoulder. It is different from most of the other "improved" H&H's in that it does not blow the case out except to create a shoulder, keeping the standard taper. Kind of cool looking.

I would like to thank you know the dimenstion of the case

Here's a cartridge dwg:



MM