Does anyone know of anything that can be done to a Browning A-bolt 300WSM to allow for an increase in seating depth? The clip limits the length of the cartridge that results in not being able to seat the bullet out longer.

Are you trying to reach the lands or gain more powder space?

If you are wanting to reach the lands, then the throat can be closed to provide a more useable seating range within the length of the magazine box. If you wan't to gain more room for powder, then I don't know off hand (I don't have one on hand to measure) what you can do with that particular length action, other than make it a single shot.