a very good round. It was the 7mm mauser necked to .25, iirc. Good velocity and power, good bullet selection, decent availability, etc.
I'd like to point out that the 06 was necked effectively to 25 and sold well. the .257 was created. In spite of the .243 and 7mm-08, nobody ever bothered making a .25-08, since there were already GREAT 25 caliber rounds. .250 savage, .257 roberts, and the .25-06.