The firing pin might not reach a .45 S&W primer in a gun made for clips and Auto Rim.
Why wouldn't it?? When you cut a cylinder for clips or to use the .45AR case, you cut it so the primer stays in the same spot relative to the breech face. done right, there is no extra "firing pin reach" involved.
Personally, I'm not a fan of clipping revolver rounds that don't NEED it. (meaning rimmed rounds).
It costs $, there is no practical advantage over speedloaders in the real world and while a possible SLIGHT speed advantage in the game world, I would think one would need to a top tier level competitor to realize any advantage.
Also, if you're looking at doing it with a top break revolver, (and, in this case a single action top break revolver) full moon clips will not "automatically" eject, you'll need to "dump" them by twisting/tilting the gun, sometimes.
Half moon clips usually will fall off one to each side, but full moons might not. Not a big deal, except where you're playing a speed game, but if you are, its something to be aware of. I base this on my personal experience with a top break revolver shooting clipped.45ACP brass. (1917 Webley Mk VI)
With the gun held vertically and opened, a full moon clip of empties gets lifted up, but not tossed out, and can wind up sitting on top of the cylinder when the ejector snaps back down. Doesn't ALWAYS happen, but can. Giving the gun a shake or holding barrel up takes care of the problem IF it happens.
I don't see where full moons are any faster than a good speed loader, but then I'm not a competing against anyone but myself. And, a top break is DIFFERENT than the standard swing out cylinder guns. You have to open the top break ALL THE WAY, to get the extractor to snap back down so you can fully insert new rounds. With the swing out, releasing finger pressure on the extractor allows its spring to retract it if the cylinder is open in any position.
I think most of the people in love with the top break revolver have never used one. They are neat, and a good design, for some things (such as short, low pressure cartridges), and they can be made to work with longer cases, but not high pressure rounds.
Specific to the Uberti, I expect it would be a good gun, Uberti has a reputation for making good guns.
I had a "stretched Schofield" in .45 Colt. Beautifully finished, mechanically crap, made by Armi San Marcos. If you have a chance to get one of those, don't. Get the Uberti, you'll be happier and have a gun that actually works right