Nicely said Trev,
Don't forget the Oxygen / Acetylene, if you can write your name on a piece of metal with a brazing rod, that you can do the same with a tig, most times, a little better. Mig for fast one-shot hits or spot welds .
Thanks.
It really does not matter what a pipeline welder would use, a Gunsmith is not a welder by trade, and has other things that he needs to know and do as well.
Key of the conversation, as far as I am concerned was the adjective 'competent'. If he is competent, he will use what he has and do a great job of it. I am pretty certain it was guntech that said he uses the Welding shop he knows. That seems reasonable, and a far better investment.
TIG is a wonderful tool, but is about the single most expensive way to weld out there. You need to stay in practice to be able to do fine work and have it come out well all the time.
If you wait to do anything, for having only the 'best' tools, you gonna die without doing any of it!
Cheers
Trev