Hamonic tunning video?

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I don't mean this sarcastically, but there really isn't much to show. Once you decide on your tuner, it's just a matter of moving it and shooting until you find the sweet spot. Hard to do on air rifles that have so much other stuff that affect harmonics, like shrouds, moderators, air strippers, etc. To really make it work in a repeatable manner, it's best with a bare barrel to which a tuner is attached. I really don't know how you would do it on an Impact, unless you strip it down to the liner sleeve and work with that. 
 
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I would also like to see some theory or tips on low HS tension and high reg pressure vs. high HS tension and low reg pressure. This might be part of the harmonic tuning process. 

My guess is that most shooters will tell you to just tune to whatever gives you the best groups. Don’t focus too much on ES and SD since 20 fps doesn’t make a difference at 100 yads and less.

I would however like to see more tuning vids or tutorials that discuss starting points for the Impact. I noticed in Ernest’s tuning video he takes the fps up to 920-925 then drops it down to 880 fps using the VSA. Some folks tell you not to use the VSA but don’t provide a reason why or why not.
 
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I would also like to see some theory or tips on low HS tension and high reg pressure vs. high HS tension and low reg pressure. This might be part of the harmonic tuning process. 

My guess is that most shooters will tell you to just tune to whatever gives you the best groups. Don’t focus too much on ES and SD since 20 fps doesn’t make a difference at 100 yads and less.

I would however like to see more tuning vids or tutorials that discuss starting points for the Impact. I noticed in Ernest’s tuning video he takes the fps up to 920-925 then drops it down to 880 fps using the VSA. Some folks tell you not to use the VSA but don’t provide a reason why or why not.
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Depending on your use, 20 fps might not make a practical difference, but it definitely makes a difference. In a high level bench rest match it would be material. 
 
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I think there is some confusion about exactly what is meant by "harmonic" tuning. Traditionally, harmonic tuning has referred to methods of altering the barrel vibrations upon firing, referred to as harmonics. This has long been a method of obtaining precision accuracy with rimfire rifles. It is simple in application, and involves varying the amount and point at which a certain amount of weight is applied to the barrel, usually in the form of a tuner that attached to the muzzle and has a micrometer type adjusting collar to change the way the weight is applied to the barrel. I thought the OP was asking about this application in air rifles. I have seen this in a few bench rest rifles, but I don't think it is nearly as prevalent as found in rimfire rifles. And one reason, I think, is obvious. So many air rifles today have so much crap attached to the barrel, that consistently applying tuning weight would be very difficult. It seems this discussion is more concerned with the normal tuning of hammer spring tension and air pressure at the port, which I would not consider harmonic tuning specifically, but maybe I'm just out of touch. 
 
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Having a movable weight on a barrel is just one way of doing it. The reason it is more common among powder burners, is that there is less options than on an air gun. Probably the simplest way to harmonic tune an air rifle is to adjust the velocity up or down, on the hammer spring adjuster. And by that, I do not mean to only find the lowest ES trough a chronograph, but rather to find the speed which has thigtest grouping on the target. If you also can adjust regpressure on the gun, you have even more options. To do a similiar thing on a powderburner, you probably has to try allot of different ammo (which is more based on luck), or hand load the cartridges yourself (which Matt dubber has a great video about). That can be an expensive process. Many airguns have allot more options built into the gun itself, to tune with, than a powder burner has.
 
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I'll take a shot at what harmonic tuning means to me. (This is from the rimfire point of view, weight on the end of the barrel and micrometer adjustments). 

What I was told the barrel acts like a tuning fork. Constant up and down motion. You want the bullet to exit when it's in the center. With rimfire ammo your set to a constant velocity. For the ease of discussion lets say my gun shot X ammo at 1050fps, but not great. Since you can't vary the velocity from the powdered stand point with the tuner you can adjust the barrel harmonics. Basically with the tuner your changing the barrel length to get the barrel in the proper position. (Center of the wave). 

In air rifles I think it should only be a matter of varying the velocity a few feet per second. Till you reach this node. I might be all wet on this but I thought that was one of the plus points of an Impact the Micrometer bumper adjustment?

Side note, the liner indexing has me curious also. I really can't see how this will help with harmonics but I can see where it will change how the projectile leaves the barrel.

If you get right down to it. Some other things to look at is liner tension. How tight you pull the barrel from front to back. Then there's the oring placement it in your barrel (so to speak) if it is vibrating. 

Great thread if you can't tell I've thinking about this some.


 
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I'll take a shot at what harmonic tuning means to me. (This is from the rimfire point of view, weight on the end of the barrel and micrometer adjustments). 

What I was told the barrel acts like a tuning fork. Constant up and down motion. You want the bullet to exit when it's in the center. With rimfire ammo your set to a constant velocity. For the ease of discussion lets say my gun shot X ammo at 1050fps, but not great. Since you can't vary the velocity from the powdered stand point with the tuner you can adjust the barrel harmonics. Basically with the tuner your changing the barrel length to get the barrel in the proper position. (Center of the wave). 

In air rifles I think it should only be a matter of varying the velocity a few feet per second. Till you reach this node. I might be all wet on this but I thought that was one of the plus points of an Impact the Micrometer bumper adjustment?

Side note, the liner indexing has me curious also. I really can't see how this will help with harmonics but I can see where it will change how the projectile leaves the barrel.

If you get right down to it. Some other things to look at is liner tension. How tight you pull the barrel from front to back. Then there's the oring placement it in your barrel (so to speak) if it is vibrating. 

Great thread if you can't tell I've thinking about this some.

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Problem is there doesn't seem to be any "ease of discussion" here. Harmonic tuning, to my knowledge, CAN involve barrel weights but CAN ALSO involve changing velocity/power which will also impact vibration. You can't reload rimfire but there are various power level loads available.

When I was shooting long range PB rifles in the 70's we often found the best groups at the upper or lower limit of the group movement that was noted with powder charge changes. Common thinking at the time was that the muzzle was moving slowly/then stopping/then reversing direction at the extremes and would thus spend slightly more time in a narrower position range at those extremes than it would near the middle of the movement range and thus would produce better accuracy. But who knows, it could have all been recoil based.

The FX liner issue seems to present a whole other can of worms. More harmonic movement with fewer o-rings? Does liner harmonic match sleeve harmonic? All very interesting but it can make your head hurt.
 
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