Ruger quit making the PC4, but I really like mine.
Bolt face has to be opened and the feed ramp modified in addition to the new barrel.
I also find it helpful to do some polishing of the extractor.
The main factors for accuracy are the quality of the barrel and proper head-space.
Unlike a semi-auto the bolt does not float, so head-space must be properly set with gauges.
Buyers are sending me pics of their targets, some are getting better accuracy from my 9mm conversion at 50 - 100 yards than many here have in .22 TCM!
9mm works very well.
.40 SW is OK but the magazine may have to be modified a bit for rounds to sit high enough to feed reliably.
10 mm can be made to work but requires some clearance of the right side of the action and a bevel to the bolt face in order to eject well.
10 mm is a pretty fat and long round for this action.
Same need to widen the feed lips as .40 SW.
Due to Armscor apparently abandoning the US market I will only be doing four more 9mm conversions.
May sell custom barrels for owners to do their own conversions.