I have a Vortex Venom reflex-type red dot on mine and it's well matched to the gun. One other change I made was to add a Picatinny rail section that mounts in place of the factory rear sight and lets me mount the red dot there. The dot is very fast to pick up and, since it is mounted on the barrel, there can be no zero change when the gun is taken down for cleaning.
The rail is sold by Taccom and is only $20. Here is the link:https://taccom3g.com/product/ruger-pc-carbine-rear-optic-sight-mount/
BTW, Taccom has several other options and enhancements for the Ruger PC Carbine