Most errant shots (not in expected group) shots are NOT really “fliers” in the statistical sense. Few shooters realize the true group size of their gun/ammo/shooting process, and instead tend to think the small, tight groups seen with five shots is the norm.
To realize the true capability of your shooting setup, set your sights so the shots fall somewhat away from the aimpoint of a target 25 to 30 yards distant and fire 100 carefully aimed shots (don’t chase shots). Compare the groupsize with typical five shot groupsize. The AREA of the 100 shot group is likely over six times the five shot one!
So realistically, ANY five shot group from the same gun/ammo/shooting conditions might have shots as wide apart at the worst seen in the 100 shot group at least once in awhile with NO fliers!
so whats a flier? Its one with a likely “assignable cause”, like:
Pellet from wrong model or caliber mixed in.
Trigger finger slip
fly landed on nose
pellet loaded backwards
earthquake
In other words, a likely event known to not be a normal part of the process. I knows its common to call most wide misses fliers, but this tends to make them seem normal or beyond the control of the shooter, whereas if the 100 shot test is done, its possible to either accept the true process spread or even `troubleshoot and refine then process to significantly improve the 100 shot ability.
Suppose you fire a shot to determine zero, and shoot at the first shot hitpoint, only to discover the next few shots are far from then first? Might be normal, so you need to fire more shots to establish a probable center based on averaging the shot pattern.