Since tuners are becoming mainstream and 2021 will be the year of the tuner has anyone done the math.
We know the length and stiffness of the barrel /contour and it’s material.
We know the weight and distance the tuner moves per setting/rotation.
Has anyone actually sat down on a spreadsheet and figured out the weight/distance formulas.
After that’s figured out there is no more debate over if a particular tuner works or not on “your” rifle.
X-weight has to move y-distance for this barrel length/contour.
I would think after that, tuners can properly be sized for the correct/particular barrel specs.
These are not one size fits all accessories.
I thought I would add my thoughts around how the tuners might work. I am replying to this comment only because it's kind of where the that part of the discussion kicked off.
Firstly I will say that I am not an expert on barrel dynamics or internal ballistics, but I have spent a significant amount of time working in fields that are concerned with the behavior of metal components and structures responding to high speed loading events (what happens in a gun).
The most basic effect taking place as soon as you ignite the powder in the case, is that the sharp rise pressure in the chamber causes elastic (hopefully not plastic) stress waves to begin traveling through the barrel and action. The speed of sound in steel is roughly 5150 meters/sec, it's actually around 5000m/s in most metals and stiff composites. I used GRT to tell me that a 120grain projectile from a 6.5 Creedmoor will take about 1.35 milliseconds to exit a 24 inch barrel (all subject to load etc.) In this time, information could have gone from the chamber to the muzzle and back almost 6 times. But this is more of the micro behavior, the macro behavior is the result of all that stress information pinging back and forth along the barrel and action/stock. Especially for long thin structures light skyscrapers and rifle barrels there are a number of what are called "mode shapes" that the structure can take when oscillating. Mathematically there are actually an infinite number of mode shapes, but in reality the energy associated with those higher modes is probably irrelevant for most circumstances. Check out this video to get a basic ideal of what I am talking about
. The difference between the video and a rifle barrel is that the rifle barrel is much stiffer, it doesn't have discretely lumped masses, and oscillations are not being induced in a dominating 2D orientation of the loading (among other things). But the principal is the same. Depending on the loading, the stiffness and the mass distribution of the system certain modes will carry more energy than other modes and the behavior of those modes will be dominating the displacements of the barrel in 3D. One thing the video doesn't show, but that would certainly be possible to demonstrate in the setup, is how changing the mass at one point can affect which mode shape dominates as well as what the displacements are. I think that is basically what the tuner is doing, it is probably manipulating which mode shape is dominant if it lumps more mass on the end of the barrel than would have otherwise been there, but more importantly, by moving the mass you are changing the mode shape. Changing it to a condition that is more favorable/repeatable for consistent bullet release from the barrel crown.
An additional aspect to consider is that part of it is timing, as I said the stress information is moving around your barrel/action/stock system at 5150m/s, so the ideal conditions at the muzzle of the barrel are surely changing with time. Moving the mass or changing the load or changing the seating depth or changing the neck tension could slightly change when the bullet leaves the barrel, relative to the conditions at the muzzle, and whether they are favorable or not.
Could we calculate/model all of this with any degree of accuracy to predict exactly what the barrel was doing for a given action/load/bullet/etc combination, so we could know right where to set the tuner before the shot? No, (absolutely not, not even with a super computer and the current state of the art numerical tools, at least not IMO)
Could we calculate how much mass you would have to move forwards or backwards, by how much, relative to the end of the barrel to be able to change the vibrational behavior (mode shapes) of the barrel? Yes, (or at least I think you could). Running some finite element models, making some assumptions, and playing around with adding mass to the end of the barrel and moving its position could probably start to give you an idea.
