I have the 20" Octagonal barrel in 45 Colt. I've been loading up some real bruisers to stretch it out. 340 gr LFN over 21.5 H4227 at around 1,270 will get anyone's attention. That is the upper end of the Ruger/t/c data from Hodgdon, not for replica pistols at all!!!.
I prefer the 6.3 Red Dot under 230 gr LRN at about 950 for dinking around.
I am in the process of adding the Marbles sights as well. Have the tang peep and a gold dot front installed, the fold down rear was back ordered but on it's way. Turns a $460 gun into something over $600, but makes 100 yard shots more doable.