Tests that we have conducted indicate that:
Each rifle has an optimal speed range in relationship to the pellet used and this ideal range changes when the ingredients change (such as the pellet)
That means that a rifle that is hot today using a 4.52 pellet batch 098 at 786 fps will need to be adjusted to 765 fps when 4.51 batch 093 are used and so on.
What happens it appears is that at a certain speed turbulance is encountered causing destabilization of the pellet. At say 786 fps everything is fine and then a pellet leaves the barrel at 795 and this phenomena appears.
It seems that the sweet spot is about 17fps deviation with the ideal setting for a particular combination adjusted to the middle of that range. This is not conclusive though.
Furthermore it was found that 5 shot groups prove virtually nothing and the minimum grouping should be 40 shots.
Using any other pellets than those sourced from JSB might be a waste of time ie. sub 800fps adjusted rifles---heavier pellets are a must for the higher speed rifles and the H& N brand also features in that range. There might be others.( Field Pellets)
Barrel harmonics and other factors were not dialled into this experiment. Only the variance in pellet and velocity were taken into account.
A one holer today might be a dog tomorrow! This continual striving for perfection makes shooting a very interesting past time sometimes frustrating too!.