That weld is 4 welds.
2 tacks, and then two beads running along the lug sides.
Done with a mig gun on a jig. Mild steel wire.
Since the material below the weld is very thin, the gun is aimed at the side of the lug to put enough heat on the lug for fusion, but not burn through the tubes. More of an overlap onto the tubes as opposed to a full wet out situation. I don't see a ribbon of silver next to the bead.
An inch on each side of that lug would give substantial purchase. Like in the thousands of pounds to tear it loose. Taking a section of barrel with it.
The little dimple at the ends of the welds with the spot in the center is a dead give away for a shop wire weld where the operator didn't let the gun cool the weld after releasing the trigger. You have to let the gas patch cool the puddle or it dimples.
I'm guessing there was a time/production constraint regarding welding model 24 barrel lugs.
I think Mr. Fox misspoke. 5/32 takes at least 150 amps to run, and even on my best days, I would never weld a thin tube with 5/32. I hope he meant 3/32, and about 55-60 amps.
At Ford Rouge Steel (Severstal) I once poured 50lbs of 5/32 7018 rod (with flux, almost 3/8" dia)into the sides of a run-off trough in 1 shift. All vertical stringers. 9 stringers deep. 5/32 typically runs 3 rod widths in puddle, so a 3/8 to 1/2 inch wide puddle is typical. As fast as I could run it (never lifting my hood between rods changes), the guys running LN-25's with innershield wire walked away from me.
