I have been puzzling over an observation I make every time I work up a new cast load.
First, the group tends to rise and fall with the load - not too tough to figure - it's a function of recoil and when in the recoil movement the bullet exits the barrel.
Second, the size of the group varies with the charge. Again not to tough to deal with - just pick the smallest group.
But in the process of watching which groups are large or small and whether they print higher or lower I've noticed three shapes of groups - a scattering, - a horizontal or a vertical shaped grouping.
Observable in 3 or 5 shot groups.
Dr. Mann had some things to say about the resonance of the barrel.
Anyone else observed this?
AND, most important, is there a correlation with size and shape of group? I.e.: does the smallest group lie between a horzontal group and a vertical group? Or ...