How can i overclock my gigabyte 760

[powerzone]

I bought a gigabyte 760 2gb oc and i try to overclock this card

i put the vcore on 1.2 max vcore
power target 110%

and i add 50 mhz on coreclock and 50 mhz on memoryclock .. when i do a test on 3dmark or playing . in a few second or minutes it tell me the driver stop working.. what happen ?

 

[Tradesman1]

Power target may be too high or not getting enough voltage, take it in small steps, gradually work it up