scout_03 :
use the auto and you will be safe .
Yeah, but from what I've studied, overclocking the core clock and memory clock using MSI afterburner is completely safe for our cards. Currently, I've overclocked it without touching the voltage. I ran Furmark for 3 hours and it passed. As it runs only on single core, I played my favorite game (Watch_Dogs, obviously) for 2+ hours to make sure my card is stable even after overclocking and to be very fortunate enough, it passed my stress test.
Since then, I went curious to know more about the overvolting. But, as you said, it is a procedure to kill the GPU instantly. That's why, MSI afterburner locks up the voltage option by default (Can be enabled manually from settings). The only thing that is set to auto is the fan speed and of course, the voltage too.