A tuner being used AFTER the PROPER load development in a conventional fashion and then using the tuner to make micro adjustments to maintain the tune is being used for what it is designed. There is no in between ground within the intended purpose even though a tuner may help ANY given load.
I think this is very much where the water gets muddy and is part of the problem there is between shooters who swear by tuners and guys like Bryan Litz who are sceptical.
Its been said many times that a tuner wont really improve an already perfectly tuned barrel, that is right for a given moment in time or a given set of atmospheric conditions. I get it that the SRBR guys do this then use the tuner to save changing powder loads as the conditions change but that isnt the only thing tuners are used for, rightly or wrongly. Once your barrel is in tune and shooting small well shaped groups a small adjustment on a tuner (how small depends on the tuner weight, the thread pitch and the increment size and even what its made of to a lesser degree) will allow micro adjustments in harmonics in the same way a very small change in powder would, thats the world of SRBR. Im cool with all that. I very much doubt Bryan Litz would disagree with any of that.
The problem as I see it is the way tuners are making their way out into the hands of your Average Joe to be used on all kinds of guns and with very little help or advice being given. I look at people testing tuners regularly on Youtube and its obvious they dont know what they are doing. Some have what looks like success when in truth its not but they dont realise and others just have outright failure and confusion.
In my mind the main man at the minute for tuners in terms of just notoriety and access for Joe Average is Eric Cortina, I dont know the guy and I certainly dont endorse anything he does anymore than I would anyone else.
I havent seen anywhere EC giving any detailed advice on how to use his tuners and/or what they are realisticly capable of. He says three shots and move, three shots and move then ultimately split the difference once you can se a node but no mention of conventional powder and seating depth tuning on reloads. I see guys using them to try and tune rimfire ammo, factory ammo of many grades and reloads, some have success, some fail and some are left undecided.
Undoubtedly it is in this context (not the SRBR crowd) that Bryan Litz felt the need to test and comment, I very much doubt he would tell a many times decorator BR shooter they didnt work when they guy is using them to win. It is to the regular guy he plays and why he will have decided to test the theory, sadly he got it wrong.
Why does that bother me? well because Ive tested tuners a lot myself and am still testing them on all kinds of guns outside of the SRBR world and I think they can be of benefit to different types of shooter in different ways, we saw that with the Browning BOSS system a while back to some degree.
The reason I started this discussion was in the hope of discussing the aspects of tuner use outside of the SRBR crowd, the good and the bad, the reasons why we see success and sometimes why we dont which I have my own theories on. For example; sometimes a tuner shrinks group but then doesnt repeat.
So, if anyone can see outside of the SRBR world and look at things in a more general context with an open mind of the different levels of improvement that can be made using a barrel tuner then we might have a conversation, if not Im happy to just slide back under my stone.