Yea barrel measuring is not easy. I got into it with the Model of 1917 Enfields. 5 grove right had twist from the Brit decision/experience for better accuracy and wear (something to do with the Cordite method of propellant I believe.
It also takes skill to use a micrometer as too little pressure or too much can distort readings easily by .001 or .002. And chambers can be a problem as the common method is to use the rounded spring loaded gauges and then transfer that via a micrometer reading.
I have seen machine shops that have a direct reading gauge for that work, has to be seriously expensive and not what you would have yourself.
Easy to see where you would likely be off in measurements not to mention the true centering issue and what distortion in the mfg of the cylinder is. Stacking error could push that off too far and you do not do any good or make it worse.
I am still pondering what I want to do with the two shooters I am going with (ROA and the Uberti Walker). Good news is they both shoot ok at my preferred distance of 25 yards. Still rested is 3-5 inch groups. Some improvement with a bit better rear notch vision on the Walker and maybe larger grips on the ROA.
Probably be fortunate to get it down to 3 inches. I hand rest for accuracy testing as I want to know what the guns can actually do a lot better. Being over 70 does not help in the standing position. Its not that I can't do it but not as steady as when I was younger and doing grunt work. Good muscle lock if not true skill back then. My step dad had the skill as he had moved up to a manager position then. Not a wimp by any means but nothing like working 10 hour days 6 days a week at true hard labor to build muscles.
Then take it to 10-15 yards for hand shooting. Walker should be a bit wild when I do that. It really needs a stock and a fore arm!