This condition is pretty common. Whether or not remedial action is required depends entirely on the individual gun and how bad the pitting is. I think it would have to be really severe for it to effect function. I've shot a number of DRs with pitting as described, and have never encountered a problem.

Of course, it can be repaired by tigging it up, using a proper heat sink, and re-facing the action. This will anneal it, so the action will have to be recarburized.