In the short range CF game, in the varmint classes, there is a rule that governs the maximum size of different parts of barrels, diameters, taper, minimum length, and in that corner of shooting competition it has been determined by at least one winning shooter, whose record speaks for itself, that a tuner may be used differently than most would suppose that it would or should be. Through trial and error, an initial setting can be arrived at, at which point the setting is locked, and further tuning done using conventional means. Gene Buckys has done very well using this method, and of course others have done well without a tuner. Buckys says that he has not found that a tuner will improve the peak accuracy of a given barrel, but that its advantage lies in its broadening tuning loads, which of course makes keeping ones rifle in tune through ambient condition changes...but that is with rifles that are designed for short range.
Having reviewed those facts, let us jump to the published work of one Varmint Al, a very bright fellow whose work tended to revolve around what is commonly called positive compensation, setting up a rifle barrel so that lower velocity shots exit the bore with the barrel pointing higher than higher velocity, so that the vertical differences in points of impact are less than would be produced by ES alone. In that work (Varmint Al's) He described three methods by which positive compensation could be achieved, hanging a weight at the muzzle so that the rate of muzzle rise was slowed to the point where bullets exited while it was on the rise, lengthening the barrel to accomplish the same thing, and making the barrel less stiff in the middle by reducing its diameter in that area.
I mention his work to point out that long range rifles generally incorporate one of these methods, a longer barrel. This is not to say that a movable weight would have no effect, but to point out that its sized may not have to be nearly as great as would be needed for short stiff short range barrels. Yes, this is merely unproven conjecture, but if we ban all of that, think of how few posts their would be, and how much less opportunity for creative disagreement ;-)
Now to the question, the point of the post, have any of you, or anyone that you know of experimented with more subtle weights at the end of typical length long range barrels, anyone except Erik Cortina? When you think a bit about his design, the amount of weight displaced is really quite small, being limited to the amount that the barrel diameter weight extends past the crown.