Moa at 500 yards is a circle with a radius of 5", or a 10" group.
Not where I shoot. A minute of angle hereabouts represents a circle with a DIAMETER of approximately 5 inches at 500 yards.
I really doubt Creeper is shooting in the "teens" on a hardware store sight in target as illustrated. It is printed for convenience with a hunting rifle. I get what he says about the simplicity of alignment but you don't get that where score is kept.
I agree with Slamfire and Creeper. Good target shooting is done with high magnification scopes. I do not understand the frequent recommendations for 3-9 and 10X scopes on inanimate targets at considerable ranges. Those are for hunters and snipers with entirely different needs.