Local gunsmith.
 

I was talking to a local gunsmith today and he said that he could take the barrel out of my original upper, weld the pitting on the upper, remachine it and then re-install the barrel and the gun saving the original upper and it would be safe to fire. Does this sound right to you guys? I thought the upper was heat treated and that welding on it would destroy the heat treating making it unsafe to shoot. He also claimed he restore the barrel to new condition getting rid of the pitting on it, again it would be safe to fire afterwards. Now I'd love nothing better then to have my grand dads Luger be able to remain numbers matching but is this guy on the level? I don't want to give him my grand dads gun and him to not be able to deliver. I guess I'm just terrified to turn it over to someone who says its "no big deal" to weld the upper when I was told by several of you guys that it IS a big deal.

Pitting repair prior to refinish is usually accomplished by TIG welding. This method utilizes only small spots of localized heating to accomplish the weld. It is much less damaging to heat treated metal than the old rod and acetylene welding system or even "stick welding". If your gunsmith is familiar and proficient with TIG welding, there should be no problem.