Bob,
I recently finished a welding a crack in a set of Parker barrels that was about 5/8" long. It was the right barrel. Looking at the muzzel the crack was at the 7:00 position and I had no problem with the ribs coming loose. I used mild steel (70S3) filler wire. I have filled pitting many times and only use mild steel wire. When filling pitting the bottom of the pitting needs to be as clean and rust free as possible to prevent porosity from developing in the weld puddle. You may also want to use a heat sink (copper is best) if you are in a thin section of the barrel. I would not personally use a MIG welder to do this job I beleive it would be a disaster. That does not mean that there is not someone who could do it that way but make sure he has really done it before you let him near your barrels.
Bill G.
