The Rubik's cube example is for the volume of the spheres packed in it, not the volume of the cubes. I have handed this over to my collection of math geniuses. Jury is still out, it's slow going as over there the moderator has to approve the posting before it goes up. First guy to tackle it assumed we were adding the shot to the ball, so I had to get it back on track.

Variation in the shot lead alloy should produce an error of no more than 1%. Irregularity of shot and edge effects would produce a larger error.

Meanwhile, I am very much with you on the question of gauge and loading. I have always maintained that if you want to launch a 12 gauge load, launch it from a 12 gauge. It seems to be an American habit that we are always trying to make the next smaller gauge do the bigger gauge's job. Magnumitis I guess.

Speaking of 9/16 oz, I have some 2-1/2 inch 28 gauge with 9/16 oz shot. (Fiocchi as I recall.) The box says 8 in the glossy print but says 4 in the little white square. So what size shot is it? (Before I am reduced to opening one. I have these for my 1911 Ithica Flues.)