Tell your graphics card to run at full power:
To change this setting, with your mouse, right-click over the Windows desktop and select "NVIDIA Control Panel"
-> from the NVIDIA Control Panel, select the "Manage 3D settings" from the left column
-> click on the Power management mode drop down box and select "Prefer Maximum Performance"
You can also tell your cpu it is allowed to use full power by going into control panel under the Power Options.
*Both these tweaks are safe and are NOT overclocking*
If it still wont go above ~60% it is most likely because it is being bottlenecked by the CPU.
The solution would be to buy a new CPU in that case.
I built my little brother a computer with a G3258 Dual core CPU and a GTX 960 2GB and the GPU often gets bottlenecked in newer games.
One other option is that something in your computer is overheating, but that is rarely the case.
I hope it helps, good luck with your components.