Reloading .303 British : Is there an Engineer in the room?

 

Yes, it was a simple explanation.  Too many engineers like to give complicated explanations for something that is really not that complicated.  The point of tuning handloads is to try and get the bullet to leave the barrel at or near the extreme of the muzzle deflection, where it is momentarily motionless; otherwise the bullets will have a variable angle of departure and variable initial velocity perpendicular to the axis of the barrel.   Stocking up can change the barrel harmonics, shift the position along the barrel where the bending nodes are (points of zero, or near zero deflection).  My center bedded No. 4 Mk I shoots differently than my middle bearing bedded No. 4 Mk 2.