Ruger does the investment castings for lots of people...and most titanium golf clubs......but they dont do the machining.
Wilson doesnt own machines to run slides and frames.
It really doesnt matter who machines them, much more how they are fitted and assembled, and the quality of the parts .
MIM parts used by Kimber...and others are sub-standard to forged and heat treated parts, fitted to a firearm. MIM parts are drop in.
MIM = metal injection molded = metal dust & glue injected into a mold, heated and allowed to cool. Very dimensionally unpredictable in dynamic shring rates.
Plastic mainspring housings are another ready to fail part...used by too many 1911 builders to save $$$.