Stan;
More hogwash than anything has been printed on the Square Load theory. I do think what Batha was citing there though was not that the entire load was equal to the bore diameter but rather that each component of it was. Thus in the 16 gauge the "Black Powder" charge would have occupied a space in the bore of .662". There would then have been .662" of wadding & a shot charge which also occupied a length of .662". Total length of the load would thus have ben .662" x 3 or 1.986" In a shell with a very low base wad this load should fit in a normal early 2 9/16" 16 gauge hull. Fly in the ointment though is that by the definition that a square load is one in which the length of column is equal to its diameter is an ounce of shot in a nominal .662" bore will stack up to around .837" long, well beyond the length for a square lo0ad which would be some where between 3/4oz and 13/16oz.
One "Noted" writer in an article I once read was touting the 28 as being great beyond all comparison to other gauges because of its square load. He then defined a square load as one in which the shot charge weighed the same as the round ball which fit the bore ( Actually a round ball equivelent load not a square one). He correctly stated this could be found by dividing 16 by the gauge number. He then went totally off the wall by saying 16/28 = .57 thus proving that a 3/4oz load made a perfect square load in the 28. Now even an old Tennessee Redneck HillBilly like me knows that .57 & .75 (3/4) AIN't the same.
A true Square Load in the 28 would be around 7/16oz. Personally I pay no attention to whether the load is square or not. Loads of 1 1/8oz in 12, 15/16oz in 16 & 13/16oz in 20 all stack up to approximately the same length. All can shoot great, none are square. Using 1Ľoz as the base in the 12 gauge a 16 with same length column would carry about a 32nd over an ounce & the 20 about 7/8oz, all still good loads again none of them square.
