Idle curiosity: does the concept of a BP square load apply to 8's, 10's and small gauges, or is it specific to 12's?
To a large extent this depends on your definition of a "Square Load". Over the years I have seen the square load defined by 3 entirely different definitions.
One definition has stated the load of shot was equal to the round ball, ie in an 8 gauge it would be 2oz. (16 ÷ Gauge "8"). In my opinion this is not the Sq load but round ball equivalent load.
2nd definition is the powder charge has the same volume as the shot charge.
This is quite often given as the Sq load concept for black or bulk smokeless powders & is I suspect the one you are enquiring about. Again "In My opinion" this should be referred to simply as the equal volume load & is not the true Sq load.
3rd definition & I believe to be the true Sq load is one in which the length of the shot column in the bore is equal to the bore diameter. This was attained with about 1 1/16oz in the 12gauge & 1Ľoz in the 10 gauge. It was seldom used in any other gauge.
It is always Hilarious to read all the explanations of the great ability of the 28 gauge with its 3/4 oz Square Load. Its doesn't come close to Any of the definitions.
With the larger bore diameter of the 8ga unless you are using large shot or just breaking clays I would suspect you might want to load a bit more powder volume than shot volume. Of course not having an 8 this is pure speculation, but from old loading info the larger gauges all seem to have a heavier powder charge in relation to shot load than did the smaller bores.
