Now all of a sudden it is 40-60 fps?
Yes, you might see a max of 60 fps in a room with no enemies, no explosions, and absolutely nothing going on that needs to be rendered besides your gun and the walls.
Even with that card overclocked to the point of going beyond stability you are not going to see a an AVERAGE frame rate beyond 45ish at 1920x1080. Every benchmark I have seen has pegged the 7850 at 30 fps average at 1920x1080 at true Ultra settings WITH fov at 90 (you move one setting down a notch you are no longer at ultra). You are not going to pick up 30 fps with an overclock (unless we are talking liquid nitrogen cooling and a massive overclock resulting in a broken card in a couple of minutes).
Regardless, your maximum framerate is not important. Your average and minimum are. If you are dipping below 30 fps then the game becomes unplayable due to screen refresh and input lag. The faster the refresh rate the better.
You may get 60 fps occasionally, hell when I had one overclocked 7870 I would get in the 100's but that doesn't mean "I get 100 fps." I get what my minimum and average are.
EDIT: Your video is also singleplayer, inside a building, at night, etc etc.... And you are not at Ultra settings...