Man...there are several on here that love to hear about what tuners can and will do and there are some that are tired of hearing about tuners. All I can say is they are a tool that I will never again shoot without and that if those people had seen what I've seen with tuners, the subject would never get old to them either. They are a phenomenal tool and to answer your question, I've never seen a weather condition that a tuner couldn't correct for...if used properly....other than wind and shooter error. That's the key to any of them. I could go into detail as to why but it bores those that already know all they need to know. I'm not one of those people and they simply never cease to amaze me!
Tune repeats over and over from extrem in tune to extreme out of tune. So even if the condition and tuner adjustment takes you to a completely different vibrational node, it will still work, over any temp swing I've seen.
So yes, buy a tuner. Buy mine or buy someone else's...but buy a tuner. Get very good instruction on how to use it and learn it inside and out. Instruction is the key!! Let me say that again...Instruction is the key to using a tuner.
They're not difficult to use but only follow the instructions for the one you buy, from hopefully the maker, as they "should" know their tuner better than anyone.
Using one is really no different that using powder charge/seating depth to tune with. Just having some amount of weight on the end of the bbl does VERY SLIGHTLY widen the tune window as opposed to no tuner but I do not hang my hat on that small difference. I hang my hat on learning to read group shape relative to tuner setting, just like I did before I ever tried a tuner.
If you wish to discuss them in detail, I'm happy to do so by phone and I have a test that will take you from knowing zero about using one to being off to a very good start in a morning or afternnon of good conditions. PM me and I can send you my contact info. I do not export them directly but Reloading International stocks and sells my tuners. --Mike Ezell