While CNC equipment has helped the small gunmaker as the article says, it’s just that CNC equipment exists. After all, CNC equipment has been around the US machine industry in ever-larger numbers since the 80’s.
What’s happened is that US manufacturing is on the third wave of CNC equipment, and now some of the older equipment is available in the used market for very reasonable prices. You can find a for-real vertical machining center (eg, a Fadal 40x20 mill) for as little as $10K. A brand-new Haas mill would run $70K, which is enough money to completely outfit a gunsmith’s shop with classic manual machinery.
The reason why the older equipment works is that guns don’t demand especially tight tolerances... so an older machine that can hold maybe 0.001” tolerance might be unacceptable in some sectors of manufacturing, but it’ll work for making guns just fine...
CNC?
Yet I work for a company that has over ten million dollars worth of extrusion equipment and they won't let us buy a vertical band saw for our shop.