The old school method is to sleeve the chamber.

The new school method is clean the pits with alcohol apply devcon steel or the MILSURP favorite JB Weld.

Both are frequently used for thAt purpose. Devcon and believe JB also, can be machined when set. After applying ream an polish.

I have pitted .303 Martini chamber to fix this way.

Devcon is amalgam of epoxy and powered steel.

Remember the pressures we talking about are per square inch. The pits are most measurable in.001's of a square inch. As a well a thickness measured in that same miniscule thickness.

What is the actual pressure on say.010 sqin. in a gun developing 18 ton psi.