It's good to see you responding here on CGN. Your experience and insight is helpful, especially to readers who may not peruse many other rimfire forums and discussions.
In any case, if they are not wrong about set and forget, it may be testimony to the relationship between tuners and good ammo. While many lots of good ammo often have overlap in ES ranges, if PC explains tuner function, tuners may well work just the same no matter the ES range. They just need good ammo to do what they can.
Thanks for the welcome. I was a little reluctant to wade into a tuner thread on my second post. I well remember the help you were when I started out with my 64MPR.
When I think of PC and the effectiveness of a tune it seems to me that most often(shooting Cx and SK) the ES is greater than what the tune can adjust for. As you know I shoot forty rounds into 8 bulls and then score for both F Class and ARA Unlimited(for chuckles) using OnTarget. I always generate one set of statistics excluding the dropped points. Occassionally that is a wind call fubar but most of them are high or low. These are most likely the rounds that would dictate my ES. Usually this subset is 37 or more rounds, very rarely 35 or 36. By this method I can compare the composite groups height and width. Most often they are close and when they have excess vertical the MV variation attributable is far less than would be expected if I chronoed.Admittedly this is a bit of data editing(read massage) but I have gained confidence in my ability to find a near optimum tune for most lots I shoot.
Some days it feels like the stars have aligned and sometimes I left wondering what the heck is up. But I have had a few very convincing instances where my tuner was not set as I meant it to be. Either it got bumped or was not reset after shooting other ammo. In every instance I was up checking the setting after three or four bulls. Of course this sort of sensitivity is much more likely for someone who shoots every day and only shoots case lots of SK and Lapua.