When someone asks a store clerk for 9 mm ammunition, generally the clerk can zero in on the customer’s needs by asking a couple questions: Target or defense? OK then, 124- or 147-grain projectiles? And, away the happy customer goes with a box of cartridges.
In baseball, there are cardinal rules that every player learns from a good coach: Never strike out looking, never give up a walk with two outs if you’re a pitcher and never be the first or third out at third base—that sort of thing. In defensive shotgunning, there are also some hard rules to which shooters should adhere.