mgallo848 :
How old is the monitor? I believe first gen HDMI was not capable of going over 60hz
If it was the monitor would have either displayed nothing or said 'out of range' when the OP overclocked it.
You can verify that the monitor is indeed running at 75hz by going to https://www.testufo.com/
I didn't know the game let you pick your refresh rate, most don't it is automatically set by whatever is set in windows. CRU edit's the registry, nvidia control panel just makes .inf file changes. I guess siege was looking for what was set in the registry for resolution.