Sliver
Since your gun is triple proofed, you might try just extending the forcing cones (according to the British proof houses that won't put a gun out of proof). With long forcing cones you'll accomplish several things:
1. You'll get rid of some of the pitting
2. You'll be able to shoot 2-3/4" shells without ruining the hull
3. Some believe long forcing cones give you better patterns.
I've done that in several of my guns and have been very pleased with the results.
It's worth discussing with your gunsmith at least.
Steve

Approach life like you do a yellow light - RUN IT! (Gail T.)