You must be very lucky then. I see it two or three times a year on average at my local range. Last time for me personally was last year with a piece of HXP brass. Mind you, .303 is the most common milsurp here and every range date will have anything up to a dozen 303s on the firing line each popping off at least 100 rounds per session, so the law of averages say its going to happen again soon.
Just dug these out of my range bag