Cases made from .303 will be just a few thou wider across the rim, which doesn't matter a hoot in the rifle action or chamber, but in my experience will eventually slacken the charger clips to the point where they require constant bending and never seem to be quite right thereafter.

Having said that, its what I use in mine, with perseverance, and a little cussing occasionally...

Just doesn't seem worth it to turn a couple of thou off each rim.