This was done with unsorted pellets.
the barrel never needed to be flitzed.
Every gun throws a flyer. Most often it is the result of ambient currents, as long as the barrel is allowing the projectile to leave, it, with consistency.
The 18.1 grain through an FX Wildcat, TRUE smooth Twist, (not a liner) is probably running at about 910 or a little under at peak unsorted velocity.,
The group in question was shot yesterday using 15,89's at a MV of 955-960 fps.
It was doped with wind current coming from, 140-165 degrees at 1-3 mph and sometimes less. Calm.
The hold off on a 1/2 inch bull, was low and right. To correct for the wind whipped spiral.
Which changed slightly throughout the 16 shot grouping. Or It would have been 1/4 inch at 75.