In his book "The Modern Shotgun" Burrard cites several verified cases of Shot Balling. One case in particular injured a beater on a driven shoot who was Well out of the line of fir off to one side.
This is much more likely to occur with card & filler wadding as they do not expand enough to seal between the end of the shell & the bore itself, particularly as the chamber transforms into the forcing cone.
This is far less likely to occur with modern "Obturating" wads, of which virtually all plastic wads are. I would personally be very cautious about using short shells with card & filler wads or even in guns having long forcing cones for that matter. The older guns with the short cones were designed so the forward end of the wad would be tight in the cone prior to the rear clearing the hull mouth in order to bridge this gap.
According to all I have read it is much more common in .410 shells than the larger gauges. I reported, on here, having experienced it once myself, on a dove shoot several years ago. The shot ball, or the entire shot charge still contained in the shot cup wad, cut the dove's head off cleanly at the neck, the head landing some few feet away from the body. It happened at a respectable range of around 20-25 yards. There was/is no other explanation for what happened.
P.S. Did a little digging and found the old thread about what I mentioned above .... post no. 377860 began the thread entitled "Freak Event on a Dove Field". Very interesting read, with many good ideas.
SRH
