"Part of doing business", anything that can happen with product liability, sooner or later most likely will.
It could have been:
Bad barrel
An owner damaged barrel
Bad / too hot ammo
The guy tried to shoot a 3/8" bolt out of the barrel
He may have stuck it 4" into the water and fired it
Maybe it was Devine provenance telling him people from Mass should touch guns
Maybe shot #2 was a squib and he wasn't smart enough to recognize it
Etc, etc.
But embarrassed people often reach for a lawsuit when they might look really stupid.
I'll wait for the evidence.