I think the point about only using a good gunsmith is well taken. As with many things, the only way to know for sure is to give them a chance though. Even good reviews can be meaningless in some cases. The garage I had my car fixed at recently had great reviews (mainly) but I still had to take it back 4 times before they finally did the job right. He had 12 great reviews on yelp and one bad one... soon to be two bad ones...
My thought was that I'd go to someone who I know does barrel work for people who shoot competitively - so they are used to needing to do a good job, not just a functional one. This way, hopefully good reviews might be from people who know what real accuracy is...
As they wouldn't be doing any permanent mods to the gun, the risk is that they ruin a blank and I end up wasting $130 plus whatever they charge to machine it. It would be annoying to waste a barrel but better than risking a whole gun.
My local shooting range has a gun store attached and they have a full time gunsmith so I was hoping to get a chance to show them what one of my best air rifles can do, so he knows what the goal is and what my expectations are.
The only way I have ever gotten powder burner guys over that "all airguns are toys" mentality is to let them try one of my good ones. It doesn't matter what I say before that, all they hear is blah blah blah I'm a little girl who shoots Red Ryder BB guns while pretending it's a real gun.
My Daystate Huntsman was the best gun (when I still had it) for demonstrating what adult airguns really are. It had that nice walnut stock and a smooth (ish) bolt-action plus a look that is familiar to powder burner users. It looks like expensive kit and not like a paintball gun in any way.
The other point is that I would only get work done on my cheaper guns so I can get more use out of them. Ernest lives 20 minutes drive from me so, for any of my expensive guns, I would get on his waiting list and be patient instead.
My my hope is that it would have to be a seriously terrible gunsmith who would make a LW or TJ barrel perform worse in my Hatsan AT44 than the factory barrel....