I don't want to start a fight here, but four very competent open top gunsmiths all agree that the barrel should bottom out on the arbor when the barrel just touches the frame.
Both Uberti and Pietta are fully assembled kits that need improvement for reliability. If you are satisfied with problems when shooting that is fine with me and blaze away.
But to paraphrase Hondo lane "Man ought to do what he thinks best".
Personally I am puzzled why Uberti, who makes a pretty good gun kit, will not reprogram either the arbor lathe or the barrel CNC machine and do what Pietta, a better made gun kit, already has done on arbor to barrel fit.
All of my open tops, which are very reliable, have such things as arbor length correction, forcing cone angle correction, cap rake, bolt timing and shaping, hammer stop, hand spring and plunger modification, lightened main spring, wire trigger and bolt spring, Slix Shot nipples, and barrel to cylinder gap corrected.
Perhaps I am just picky but I want a revolver that works every time I cock the hammer press the trigger.
Anything less is aggravation and frustrating.
YMMV
Bunk