Not sure about the shore but for any lathe work I don't want to do myself I use Ed "doc" Harren of harrens custom rifles. He's in ijamsville on the the Frederick/Montgomery county line. Great benchrest smith who also turns out very nice Varmint and target rifles. Shot some of his more tactically oriented work and they shoot like his bench guns (til you get them too hot!).
with all the prevalent prefits out there, consider putting something together yourself. i have a bighorn tl3 6.5prc and a tikka t3x 6.5 creed both with proof carbon shouldered prefit barrels and they are both very accurate. action wrench, barrel vice, torque wrench and you're pretty much there. i will say it was a bitch getting that factory tikka barrel off, but if you're just starting with a bare action you won't have to deal with that.
What do you mean by a "custom bolt gun"? What exactly is it you want "built"?
- MOA hunting rifle?
- PRS competition rifle?
- short or LR benchrest rifle?
All very different.
Rebarrelling an off-the-shelf rifle with an off-the-shelf pre-chambered barrel, or bolting an action and pre-chambered barrel into a "chassis" is quite different than building a custom rifle. But may fit your needs. (Yes - Ed Harren BUILDS rifles. To BR standards.)