If I have a lite contour barrel, I’ll have it sent to Kampfeld Customs and have it cut 5/8x24. Karl Feldkamp does excellent work. His work is particularly nice because he adds a false shoulder that most smiths won’t do. This was a 9.3x62 that another smith insisted had to be 9/16x24, which would require an adapter.
I had this .270 done by a local smith. I wanted it 20” and 5/8x24. He took three months and gave it back to me 21” and 1/2x28. He said cutting it to 20” would have required removing the barrel from the action. He did good work, but I had to roksett an adapter onto it. Karl would have done it the way I wanted it, faster than the local guy, and for less money.
For a heavier barrel contour, I have sent them off to Silencer Central and had good results. Their door-to-door service is pretty speedy and they do good work. They did a very nice job on my heavy-barreled .25-06.