as you quite rightly say, its lock time, which is in milliseconds. its not going to be the same every time, but its going to be close.a pellet of a given mass, co efficient of friction, design, will accelerate at approx the same rate as another. voodoo no.a fully floating barrel is a cantilever. attaching a mass to exert a force in newtons upon will have an affect upon the harmonics.
put 100gram weight near breech/fulcrum point, it will have little affect. move it along the barrel toward muzzle the effect will increase. at some point a sweet spot will be reached. put money on it that that will be close to a node.
the muzzle velocity will vary shot to shot but not enough to dramatically alter the effect. at the node barrel stationary, close to it accerating/decellerating slowly. at mid point in cycle at max velocity of the movement/harmonics of barrel. if pellet exits around this point the result will be applified by any varriation in exit point/ muzzle velocity.
i'm not perfect, but I shoot FT, reality is this is pretty much the same thing!