The blue shell in Drew's second picture is what mine looked like - I called it "pinched" and Drew called it "feathered" but the result is the same no matter what it is called.

Mine were 2 3/4" factory AA with #8 lead shot at the trap range... and I shot a lot of them back then. These days I reload 16's, 20's and 28's and generally buy my 12's from Morris, or bum a box from a friend if I run low.