Contrary to popular opinion, CNC machining aint the end-all, do-all that it is cracked up to be.
All machinery is subject to things like tool wear, fixture wear, chuck wear, way wear, differences in coolants and coolant flow, vibrations, incorrect leveling...and on and on.
And FWIW, it aint uncommon at all to bore, ream or drill more than one hole using the same set-ups....and end-up with slight differences in hole-size.
In fact, if you're after absolute uniformity, it's probably best to drill the dern hole a bit undersized and the finish it with a hand reamer.....sure is slow though.
As far as not having guns to ship or parts to fix a certain gun....I aint surprized at all. Ruger has long been known to anounce a new gun way before they were ready to fill a lot of orders.
On top of that, it is said that Ruger makes guns in "batches"....as in, they'll make a bunch of a couple of models and then switch production to other models....mostly decided-on by what particular model has the most pending orders.
Almost nobody builds up inventory these days....They all been Ki-zaned and/or Five-S'd.
This aint a slam on Ruger. Most manufactures operate that way.
DGW