Blacktails is correct.
All of my stockwork begins with an uninletted blank from any quality stock manufacturer.
This is a cardinal rule of my shop.
I generate all of my inlets as a 3 dimensional CAD surface model of the particular action I am working with. It's then increased in size by .05" in every direction. All epoxies shrink. The better ones keep it down to around 1-2 percent. My bedding process ensures that the action has a uniform film of resin at every contact point. This way at least the amount of shinkage is uniform at all points.
From there the inlet of the stock is performed using a 4 axis CNC vertical milling center. I machine the inlet using specialized tooling that I either buy off the shelf/and or make or have made. (it's a significant investment) Tool paths are generated in such a way that the stock retains crisp edges at the show line (the days of wood exploding/shredding/ripping from the edges are gone for me)
I also measure each barrel individually and generate a surface model of it as well. It's cut at the same time as the action inlet. I do this a bit differently though. +.030" on the sides and +.060" on the bottom at the belly of the channel.
Here are some sample photos of recent and old (5+ years old gun in the last photo, picture was taken a week ago):
That's my story and I'm sticking to it
If you'd like to know more, just shoot me an email or PM.