Couple of things I noted from these posts. Uberti's almost always have short arbors. They use a tapered arbor to ry to limit how far on the barrel can go. Pietta uses a straight arbor and they mostly get it the correct length where it bottoms out in the arbor hole when the barrel lug meets the frame. In any case that should be the first thing checked and corrected, if need be, on a new gun. In no case should you use the wedge to adjust the barrel/cylinder gap.
Now to wedges. Uberti has the right idea. Their wedges have no taper on the flat towards the cylinder the taper being only on the side towards the muzzle. There is a corresponding taper in the end of the arbor. This allows the flat towards the cylinder to bear equally on the flats of the wedge slot on both sides of the barrel. A perfectly fit wedge will just have the radius protruding from the far side at the point you start to feel resistance. It will lock in place with a light tap and unlock the same way.
Pietta has not figured out the correct use of a wedge to lock things together. They have a 90 degree flat in the end of the arbor and tapers on both sides of the wedge. The wedge can only contact the near corner of the arbor slot on the inbound side. The taper on the side of the wedge near the cylinder allows the wedge to get through but only contact the barrel flat on that side. Then Pietta brings in Luigi the gorilla wedge setter to beat the thing in place. Fortunately all of this is correctable by the end user, but you shouldn't have to as it would be no more expensive for them to do it the correct way to start. One of my pet peeves with Pietta. I still like them as they have brought their quality way up in past years .