My own Bearcat shoots dead-on for windage for me and seems to do so with several other folks. Elevation is close with 40 gr. HV loads from most manufacturers. How close depends a lot on who's shooting. Eyes and styles vary.
The first thing I'd do given that much difference is have a couple of other folks try a few groups from a rest with an assortment of ammo. At least it'd tell you a bit about how much these factors are in play here. FWIW, I had some trouble with my groups shifting with changes in where the light was coming from relative to that shiney front blade until I painted it with flat black enamel.
If the groups are still way off for other folks too, I'd send it back to Ruger with a letter explaining what's going on and perhaps a couple of typical targets for reference. Ruger has very good CS, and a rep for making things right if you've got a problem.
I've heard lots of folks comment that they wish Ruger would offer a Bearcat with "target-style" sights a la the excellent Single Six. It'd certainly make things easier for the folks who want to use several different loads in them.
Until they do, the best advice I've got is to pick the type of loading that best suits the bulk of your uses for the Bearcat and find the brand that gives you the smallest groups. Once you or Ruger have the windage centered for it, pick a distance and start firing groups. If they're "low" you can gradually remove material from the top of the front blade, just a light stroke or two at a time, until they're centered where you want them. If they're "high", you'll have to either add more material or fit a taller blade out front.
If you pick the right load and stick to it, "fixed" irons make perfect sense for a handgun that's likely to get knocked around in its daily life - centerfire or rim. Not as convenient, perhaps, but a lot tougher and extremely practical. The little Bearcat was originally conceived as a compact working tool for hikers, campers and other outdoor types. Maybe Ruger'll hear us if enough folks tell 'em they'd like another option.
