Gene.
One question keeps nagging at me - and it's probably been covered and I just missed it some where.
You say that your rifle is never more than 1/2 a turn out of tune, and I can understand that. And if it is in tune - one full revolution and it's back in tune. I can more or less follow that. But if you turn it exactly 10 turns is it still in? 100? 1000? - where exactly are the edges of the envelope? Is the tuning "window" wider or more stable in the center of this range?
Sounds good. But 8x5°=40° and is one full revolution of the tuner, so if you last shot it in 50° temps and the next match is at a range that is seeing 90° does this mean that it should be in tune again?
Of course all of this depends on consistent ammo - so the point about having to change the tuner setting with a change in primer, powder or other component makes perfect sense to me. the MV might very well be the same but the actual time in barrel might very well be different due to a different acceleration curve, resulting in a different time of exit relative to the harmonics behavior.
Vibe, it sounds like you understand it all very well.
You asked,
"Gene, one question keeps nagging at me - ,,,,if you turn it exactly 10 turns is it still in tune? 100? 1000? - where exactly are the edges of the envelope? Is the tuning window wider or more stable in the center of the range?"
10? 100? 1000? In theory, it should be but in a practical application in the real world I wouldn't bet on it. My tuner is .500 inch in width and I only thread .750 of the muzzle which gives more than enough threads to make adjustments. Actually, you need only one revolution of threads but I like to have a little room to spare. I have used as little as .625 of threads but have settled on .750 as the standard.
When I go to the line for the first match of the day, I start with the tuner in the 'zero' position. By this I mean, screw the tuner all the way 'in' (toward the breech) then back it off until the reference mark is at 12:00 o'clock, then make one more revolution 'out' and lock it in place.
"But would it be okay if I backed the tuner out two turns, or maybe three?"
Yes that would be okay if you choose to do it that way.
"Where exactly are the edges of the envelope?"
The envelope is limited only by the threads, but you actually need only one revolution to tune the barrel any time, anywhere.
"Is the tuning window wider or more stable in the center of the range?" No.
Vibe, you also asked,
"Sounds good, but 8x5°=40° and is one full revolution of the tuner, so if you last shot it in 50° temps and the next match is at a range that is seeing 90° does this mean that it should be in tune again?"
In theory and assuming the two ranges are at the same altitude and barametric pressure is the same in both cases, yes; it should still be in tune, but in the real world things don't always work out that way, and I say, why worry about it?
As I have said many times before, you need only one revolution of the tuner anytime, anywhere and you cannot be more than a half turn out of tune. Go to the line for the first match of the day with the tuner set to 'zero.' Follow the simple procedure I outlined earlier and when you have the rifle in tune, make a note of temp and tuner setting. Then, you will know where to place the tuner as temp increases throughout the day. The formula is, turn the tuner 'in' one eighth turn for each 5 degree increase in temp. I can't make it any simpler than that.
Some will probably ask,
"Will this work on all rifles? Will it work on my rimfire or 1000 yard rifle? How 'bout my 'thutty thutty'?
I don't know; try it and see like I did with the LV and Sporter rifles.
Hope this helps.
Gene Beggs