Good advice- TIG is the best method. I'd also recommend this: Use a Tempilstick for the preheat- they look like crayons, and are marked with the temperature range- buy one that says 150 degrees, and mark the HAZ area- when the crayon turns to wax and runs, that's your temperature- In a perfect world, MIG would work, but you might want to go with a filler rod that matches the metallurgy of that lug- and a smaller dia. (.022) such as the body shops use- sometimes known as "stitch welding" for ligher gauge sheet metal- also, consider a 100% Argon shielding gas- most fab shop MIG welders set up for HSLA steels use 75% CO-2 and 25% Argon for the shielding gas and a .045 70-S3 grade wire- and be fussy about the tip and cup on your gun- clean and without spatter-you will get less spatter and a "wetter" bond of the filler wire to the parent metal with Argon-but it is way more expensive- do you have a scrap barrel lug to experiment with first? How valuable is the shotgun you want to rebuild the barrel lug on? If you have an older Davis or Crescent- sure, go ahead- but if I had a FE AH Fox or a Monogram L.C. Smith- I'd only go with the TIG process- IMO-O RWTF!!
