I would certainly think Robert Hart & Son in Nescopeck could handle this. They have a website. They have built several guns for me and the work was always top notch.
Is 1/2"x28 an acceptable substitute for 13x.75? Would this make the barrel wall too thin for a .270 caliber?
There's only .020" difference in diameter between 13MM and 1/2". That's about 10 strands of hair stacked up together. The barrel won't know the difference.
I would certainly think Robert Hart & Son in Nescopeck could handle this. They have a website. They have built several guns for me and the work was always top notch.
They had no problem rebarreling a Sako for me a few years ago.