Right good to hear.
Now could you download any stress test
http://www.ocbase.com/ is fine to use. And a application that can monitor your temps. I suggest HWmonitor.
Open the HWmonitor and run OCCT for 20 minutes at stock. Keep an eye on your temps I am starting to think your system shuts down because of the temps during high stress parts of the games you play.
To help us help you - please provide as much information about your system and the problem as possible.