I have a circa 1906 Sauer that was origanlly a 70 MM chamber length and is marked so.
I would assume yours is a 65MM chamber. I had great luck on North Dakota Phez this year using Kent Tradition Gamebore shells in english 6s & 7s - they are loaded to CIP pressure standards and should work well in your gun for pheasants.
Personally I only shoot Fiocchi Golden Pheasants in Pump guns. I do however shoot Fiocchi Game and Target loads in my older 16s - these run approx 7800 PSI or so - they are however 2 3/4 length shells.
