NVIDIA recommends GeForce GTX 970 for Call of Duty Black Ops 3
NVIDIA recommends GTX 970 and above for Black Ops 3.
For FullHD gamers, GTX 970 should be enough to handle 60 FPS at high detail settings. If you monitor is 2560×1440, GTX 980 should be perfectly capable of sustaining this frame rate. Lastly, GTX 980 Ti is recommended for 4K gamers.
Personally I quit playing Call of Duty after it became more and more futuristic. Where are the proper WW2 shooters without flying drones and super jumping capabilities?