From Post #58 - will spin you around, like it did me, to discover that you have to take into account where a writer is from - Britain and USA, for example, have different shot sizing - so what one calls "#6" is not the same name for that size shot in another country. No clue why they do that. Can find charts on Internet to compare shot sizing names used in different countries. Is likely small potatoes, I guess. My desire for my 28 gauges is to use .10" diameter shot - has different names for "shot size" depending which country it comes from. Probably like older shotshell boxes that listed "dram equivalent" for the powder loading - I do not think is used any more, but for some reason, shotgunners wanted to know the equivalent amount of some unknown-to-me black powder that used to be be used in shot shells, that gave equivalent velocity to the shot. I think "modern" stuff just tells you the velocity...
And there is some undefined dividing line between "game" size and "target" size shot - for target size, there is 1/2 shot size greater or lesser sorting tolerance. For game size, is a full shot size - plus or minus - allowed. So a bag of premium #4 shot (presumably a "game size") will have #5, #4 and #3 sized shot in there - all perfectly acceptable and within tolerance - so shot is NOT all the same size, in a bag.