Quote:
A 7/8oz 20ga load "IS" a lighter load proportionate to gauge than is a 3/4 oz 28ga load.

Well now it is quite obvious that 7/8oz is heavier than 3/4oz, but "Read" what I said, "Proportionate to gauge". And "NO" 1 oz of shot will not go into the space occupied by a 1 oz round ball, not even a cylinder having the bore dia & length to fit the round ball. "NO" Hercules/Alliant (I am using both names because this chart appeared in the old Hercules guides prior to becoming Alliant) did not include the wads, only the shot & that in an unprotected bore of nominal gauge size. Also obvious the use of shot collars reduces the dia & thus extends the length. A 1oz shot column in a .662" dia bore (16ga) will occupy about 25% more length than the .662" length occupied by the round ball. But Hey; Don't take my word for it, measure it very carefully, then come back & tell me why I'm wrong.
As to the .410 being loaded heavier, there is a term in ballistics known as "Load Density" (LD) which is Lbs per Sq IN. This refers to the projectile weight in proportion the the area of the bore. The formula for this is LD = W/D² (W = weight in lbs & D = bore dia in inches). Thus a 1/2oz load in a .410" bore has a LD of .186, while a 3/4oz load in a .550" bore (28ga) has a LD of .155. Thus proportionate to the bore dia the 1/2oz load in a .410 is a heavier load than 3/4oz in a 28ga. This is why all .410 loads use a very slow powder, they have a heavier load to lift per SqIn.
The "Proper" definition of a Sq load is still one in which the shot column length = it's dia, because it appears in crossection as a square. A Round ball equivelent is not Square. There is of course no advantage to a load being square to start with. The term is conspicious by it's absence in such notable works as Burrard & other knowledgable ballistics writers.
As to the SS mag if I get a chance to get by the book store may set & read it. Glad I was fore-warned, I certainly wouldn't want to spend any of my limited funds on such "Garbage" as that.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra