Overclocking game crashes and artifacts

OK so I just did  200 MHz over Clock on my GPU base frequency and a 150 for the memory to see how much performance I get, I've done it before but the same thing happened, and as soon as turn on crysis 3 the game starts having artifacts and then it crashes. Is this exclusive to crysis 3 or is it my gpu.

you say you've done it before? have you done it on the exact same gpu?

Not all pieces of silicon are equal your obviously doesn't have the potential to run that high.

It's the gpu not the game most likely

Voltage may be too high/low, or the over clock is unstable. 

I second that, you have symptoms of an unstable GPU.