Why not just keep count of how many you've fired.. If counting to (or backward from) 8 is hard, maybe you shouldn't be shooting a gun anyway..
Cause if the poopoo hits the fan at your house or something, you probably won't be going "1,2,3,4 OH SNAP another guy just went by my other window, 5, 6, Crap! Did he just shoot my dog? 7, 8, I better change mags now......"
I'd rather go BOOM BOOM BOOM BOOM BOOM BOOM. Quick look down while repositioning in my hallway, 2 rounds left. BOOM, reload (saves from cycling bolt). Also, when the zombie apocalypse occurs, you may bust 3-4 z