Unfortunately I don't have much good to say about the Open Top guns in .45 Colt. I have worked on a lot of Open Tops and my own main match guns have been a pair of Open Tops in .38 Spl ( Gunfighter). They are some of the most natural pointing guns I've ever fired.
All most all of the Uberti Open top guns have some issues. The most common ones out of the box are timing and the fit of the arbor to the barrel. Most need to be re-timed and have the arbor/barrel fit fixed. The hole in the barrel for the arbor is drilled too
deep for the gun to set up correctly. Once the barrel/arbor fit is fixed, you can address head space and end shake.
Once the guns are set up properly, they are a robust and reliable as any thing else we shoot in CAS, with the caveat, in any caliber except .45 Colt. Once bored for .45 Colt there is precious little meat left in the cylinders. May guns I have worked on (.45s) have spit the little piece of metal left at the bottom of the bolt slot out. Some folks have reported cracking at the back/bottom of the barrel.
I cannot recommend the Open Top guns in anything larger than .44 for those reasons. I do personally have a set of .45 barrels and cylinders for my Open Tops but I shoot .45 Cowboy Special type brass at a very reduced load.
Coffinmaker
PS: The original Open Top was chambered in a proprietary Colt .44 cartridge, rimfire that would interchange with the .44 Henry Flat, to make it compatible with the Winchester '66. The original guns were never chambered in anything else except for a few non production guns.