All of the best gun companies use CNC these days. The level of finish one gets off the machine is totally dependent on what the operator is wanting and their abilities. Unfortunately, it's not as easy as loading some steel in the machine and pushing a button.
One can get actions barrelled or not from one provider that is an ex-Purdey machinist, incredible amount of detail is done in the shaping and very little is left to do. When he machines the barrels the fitter is left with less than .004" of smoking on-face. You pay for it, but the end result for a Beesley or Woodward auctioned gun would be a 1/3 the cost of a Best name. He uses a mix of wire edm, spark/sinker edm, and 5th axis VMC.
I've seen other providers that leave them more squared. There are also craftsman working in the trade doing best quality work with nothing more than manual machines, broaches, chisels, files, etc
I wouldn't necessarily say modern best guns are better than early guns because of CNC. The biggest benefit with CNC comes when you jump to 4th axis machining, less setups are required. Obviously any CNC gives one the ability of machining complex shapes with radius, repeatedly.
Through hardenable steels have come a long way. I'd keep an eye on steels like S7 becoming more popular in gun use.
