I would imagine they're made basically in the same manner as the military actions. Why change? Under non-war time conditions, quality control is probably quite good. I have several custom rifles built on Oberndorf and DWM Mausers and some on comemrcial FN actions I even have a Husqvarna FN style 98 Mauser that will be a donor for a new .35 Whelen.
If you want a good FN action, look for a J.C. Higgins Model 50. A true FN action with barrel and stock by High Standard for Sears to Sears standards. The barrel was chrome lined and every one I've had has been accurate.
Personally, for a custom rifle, I wouldn't use anything else. JMHO.
Paul B.