I went to the range with the rifle and it shoots great. I think everyone that said the muzzle is coned is most likely right. I shot the rifle at 50 meters and got holes line up vertically when I held the windage right. When my group size opened up I think it was due to not so ideal sights installed. The rear sight is a tiny little V notch - probably 20-30 thou at the widest and 40 thou deep. By itself it is not a problem, but the front sight is a huge post that is between 1/8th and 3/16th wide. It is very difficult to center the V-notch on the post . I ended up covering the target with the post (it turns out to be almost exactly the bull of the 100m target at 50 meters) and then focusing on the V-notch to align it (pretty much the opposite I normally do when shooting with iron sights).
I originally thought this humongous front sight is something previous owner put in, but having found some photos of other Pedersoli Plainsman in 38 cal online they all seem to have this sigh (pictured below)
The rear sight:
And the sight picture - bear in mind the mobile phone camera has different focal length than the eye and when looking the post appears to be at least twice the size it looks like on this photo:
So I'll either have to make, or order a blade sight for it. I would prefer original silver blade (a small bit shouldn't cost too much), but I can't find any ready made ones online. Then track of the wolf shop appears to have nickel plated blades. Can anyone comment if these are visible on a bright green background (grass etc)?
Another issue with the gun was that when the trigger was set and pressed after the gun was cocked the hammer moved a tiny bit and didn't fall one had to set and press it again to fire. Upon disassembly I found out the notch the seer rests in on full cock became gouged and the seer was stopping in that gouge when it was pressed once. Second pressing released it. I fixed it by filing the face of the full cock notch.
Finally, the nipple installed had a much larger hole than new nipples I have in my other rifles. The hole looked like it could be around 60 thou. Even with 20 grains of powder the hammer was blown to half cock. I replaced it with a new nipple with a regular hole and now the hammer stays put on the nipple when the gun is fired even with 60 gr.