I think it would take a lot more time to bring the base metal and filler rod up to fusion temperature with a small TIG tungsten than it would to touch the MIG wire to the side of a screw hole and give a quick shot of the trigger. It might take 2 or 3 shots to fill the hole, cooling the spot of weld between shots. The heat absorbing paste I referenced above is pretty remarkable stuff. I have filled small holes in both sheet metal and heavier stock and had the heat (tempering colors) run very little. Yes, I know blue heat color running much more than 1/8" is high enough to melt solder. But I still think the heat control paste might prevent melting and seperating of the solder joint. I imagine one could go a step further and fill both barrels with cold water and then plug both ends. Ever try to solder a pipe with any water in it?
I'm not willing to bet the farm yet, but I really think this would be possible. On the other hand, I agree that just putting the sling swivels back on would be the easiest, cheapest, and most appropriate solution for this particular gun.
