the term CNC is also used as loosely as polymer.Especially in airsoft.
Just as all plastics are polymers; not all polymers are created equal,
Not all CNCed metal is equal.. and not all CNC process is what you think it is.
There's cast parts that are finished by CNC... pot metal with machined finishing to get in certain things... such as a computeriszed drillpress to cut in the pinholes.
Then there's CNC out of BILLET. which is a single piece of material, be it polymer, brass, wax, steel, what have you.
They take a piece of solid stock and the computer guided machine cuts your shit out of it. That would be the strongest.... that does not exist in airsoft.
However, CM plastic bodies are just ABS. there are other plastic bodies such as nylon fiber reinforced plastics/abs that are much stronger, but again, notall nylonfiber is created equally... dpending on fiber count, composition of the abs element, casting quality, mold quality, temperature control of the plastics when they're injected into the molds.. etc.
Loose tolerances are what you're most concerned about. You can make a gun accurate, but what you should care about is making it precise. To quote someone I know who was a realsteel shooter in the military : Accuracy is a product of the shooter -- precision is a product of the weapon.
Accuracy becomes easier to get when the gun is more precise. Meaning if I put the gun in a vice on a bench, at x meters it will shoot a tight, predictable grouping. Meaning that as a shooter, I can rely on the gun to put rounds exactly where I want at distances I know it can reach out a, that's where I can be an accurate shooter.
First order of business for precision in your weapon is air seal, after that it's application of hop and barrel bore consistency. Using quality heavy rounds will also increase precision.
I did not say, barrel bore diameter, hop up unit or barrel length. These have not shown any definitive indication that a gun is more precise in the dozen or so guns I've built for people this year, or the other countless guns I've worked on for other people.
Unless there is something malformed in those components, there's no reason to change those parameters.
My 30$ madbull python 247mm barrel shoots as precise as my 80$ prometheus eg 407mm. Both are able to put rounds through car windows or hut doorways at 70-80m on target.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.