R9 270x Overclocking issues

I have a R9 270x wind force edition. I bought it on ebay for about 120$, It was in Good new condition, you could not tell it was'int new. I believe it was previously used to mine bit coin for just a little, I tried overclocking it with AMD overdrive in the catalyst control center and i tried overclocking it with asus gpu tweak, When i preform a slight overclock, for example to 1300mhz, any game that i launch and even in windows everything freezes, subsides and then freezes over and over again until i disable the overclock. What do i do? Maybe the gpu bios is fucked up? how do i refresh the Gpu bios? Should i use the gigabyte overclocking utility? What am i doing wrong?

Well, actually this card is known for its overclocking capabilities, People are usually able to get 1400mhz pretty easily. And usually the side effects of over-over clocking are overheating, shutdown or crashes, not this weird micro crashing 

Umm I had trouble getting past 1200 on my 7850...

Perhaps you should actually do the proper small increment + stress test to see how much you can actually push the card instead of just bumping it to a high number.

7870 is more comparable to this card.

Try gigabytes overclocking utility if it allows you to feed core more voltage. Look up safe core voltage for this card before you change shit.