Jackie,
You've almost got your finger on it with your last question. Barrel vibrations aren't the only cause of inaccuracy. They appear to be a big part, but they're not the only part. A "tuner" will make your groups consistent, "tuning" will make them small.
John,
You caught me in a lie. I find this seemingly never ending discussion of tuners frustrating. I haven't read everything that's been posted on the subject. I'm finding it difficult to wade through all these theories on how and when to adjust a tuner when I know it's a lot simpler than that. Find the right tuner setting then never touch it again. My apologies to anyone I've misrepresented.
You've put your finger on a couple of things yourself. You can't make a centerfire barrel as thin as a rimfire barrel. Not for the full length anyway. Probably the biggest source of my frustration is that people seem to want to start with a 10.5# rifle and then find a tuner that works. In my opinion, a better approach would be to find something that works and then try to make weight. Making weight is a clear and simple goal that everyone can understand.
You're also right that the slow, methodical, empirical approach I took to find my tuner setting with my rimfire won't work in centerfire. As you rightly point out, you don't have the barrel life to do that with a centerfire.
You were asking Bill for some pointers on how to know when you were close with a tuner. Freely admitting that I'm no Bill Calfee and fully expecting some flames, I'll give you a few of my observations. First though, a brief summary of the methods used. I burned through roughly 10,000 rounds on relatively calm days testing tuner settings. I have tested tuner settings at intervals of full revolutions down to as fine as five click (roughly 0.005") intervals. Some regions of the tuner were tested at resolutions as fine as one click. I have tested as many tuner settings as I could in a single day and tested smaller ranges of tuner settings on multiple days. I measured every group and allowed no alibis. Every shot in every group counted. I have made scatter diagrams of large samples of groups and graphed both average group size and deviation from the average at every tuner setting tested.
First, to prove I don't worship at the alter of Bill Calfee, I believe Varmint Al may be right on at least one point. There appear to be more vibrational patterns at work than the one Bill looks at to find his tuner weight. All of my graphs look remarkably like the sum of multiple sine waves of varying frequencies. But with enough groups fired at enough tuner settings, one setting stands out as better than all the rest.
About the time the graphs were becoming clear, I noticed that the one best tuner setting seemed to shoot through conditions better than any of the others. Not that I could ignore the wind, I just got a lot fewer of the "Whoa! How'd that get way out there?" moments and a lot more of the "Huh, I held too far for that one" moments.
The increase in accuracy from a tuner seems to come mainly from eliminating almost all the flyers. If you throw out all the biggest and smallest groups you're shooting now and just look at the most frequently occurring range of group sizes, a tuner isn't going to improve on that much. A tuner seems to narrow the range of group sizes you get but the quality of the ammo determines what that average size is.
This one is going to get me flamed for sure. In the same way a tuner seems to eliminate the big groups, it also seems to eliminate the really small groups. Apparently there's some truth to the old insult that sometimes all the flyers go into the group. There are regions on the tuner that will let you shoot the occasional really small group, but it's a waste of time chasing tuner settings in that region. I don't understand it, but I saw it often enough that I could sometimes predict it. If I had three shots in a tiny little bughole but the group was forming low and a little right, the odds were very high that at least one of the two remaining shots would be a big flyer. Not always though, on rare occasions I got a nice little wallet group out of it. If your rifle with a tuner is capable of shooting really small groups, it will do it consistently from the moment you find your tuner setting. If it's not consistent, you don't have the right tuner setting. Bill is looking for some zero aggs, but even with widespread use of tuners, it's still going to take an exceptional shooter/rifle/ammo combination to do it.
That's enough of my bs, hope it helped someone. The rest of you can fire away now.