Can any of you guys tell me what if any difference tig welding a barrel or receiver would do to the heat treatment of those items? After welding would they need to be re-treated? What if it was done a little stitch at a time?

BB

Any type of welding will make the metal near the weld hot enough to affect the heat treatment. A good Tig weld will affect a smaller area than other types of welds, but it will be affected nonetheless.

If you contemplate ANY type of welding on a rifle you need to have someone with a good background and understanding of weapons and heat treating, as well as welding, to do the job.

Gary Littlejohn (Littlejohn bicycle frames) is a close personal friend of mine and is one of the best welders I have ever seen...but I would not let him weld anything on any of my firearms.

Some things a guy likes to keep heat treated.
When TIG welding 1/2" away from that metal, heat sinks or paste work well to keep the important metal cool.