in fact, my experimental shotgun measures 0.0025 gauge (it's barrel diameter is approx. one foot), but "Zero Gauge" is a MUCH more marketable name, if not exactly technically correct.
I suppose it could also be expressed as "AAA-1/2", or some such, but "Zero Gauge" still has a nicer ring to it, don't you think?
You CAN fit an awful lot of bird-shot in each shell, though, I can assure you of that.
;-)
At 585 #9 per ounce you bet!
Did you know a .22 smoothbore could techincally be called a 500 gauge?