Here is theSource of this fix.
This fix will change the way your mouse works in-game for both your regular infantry view and when using stationary / vehicle turrets or Choppers.
Currently Battlefield Bad Company 2 has mouse smoothing on by default, with no way of turning the feature off in the game’s settings. Mouse Smoothing normalizes your mouse’s input, “smoothing out” very fast or very slow movements. The result of this smoothing is often aiming that feels floaty or laggy, which is obviously not desirable in an FPS!
Also BFBC2 turrets tend to turn at a much slower rate compared to normal infantry mouse aiming. This fix will solve that problem and opens the potential for turrets to reach their maximum turning speed without affecting infantry movement. This will also make vehicle turrets turn faster, but they have a hard-coded maximum turning speed, so don’t expect to pull a quick 180 with a tank turret anytime soon.
DISCLAIMER: This fix involves changing values within key game files that are relied upon to properly run BFBC2. It is advised that you back up these files prior to editing, and that you don’t go changing any values outside the ones shown below. Use this fix at your own risk, you assume all responsibility if you mess up your game.
Ok, with that out of the way, here are the steps to killing mouse smoothing and fixing those slow turrets:
Go to your My Documents > BFBC2 folder. We will be making changes to the Gamesettings.ini file, as well as the files within the input folder, so go ahead and make back-up copies of those first.
IF YOU DON’T HAVE AN INPUT FOLDER, IT IS BECAUSE YOU ARE USING THE DEFAULT KEYBINDINGS.
You must go to your settings in-game and bind at least one custom control (doesn’t matter which) before the game makes this folder with the proper files inside.
1. Make sure BFBC2 is closed
2. Open GameSettings.ini and make the following changes:
Scheme0Sensitivity=2.50000 <--- This value will be your normal in-game mouse sensitivity, it seems to have no effect on turrets or vehicles. Feel free to experiment with this value and change as necessary. I found 2.5 to be a good compromise between fast turning speed and precision with a 1000DPI mouse, but YMMV. Values from 0.001 to 100+ are valid. InputAcceleration=0 3. Save and close GameSettings.ini 4. Navigate to the input folder, open infantry.dbx using notepad 5. Search for the following line: ConceptPitch 6. Below this line you'll see several similar-looking blocks of data. Make the following changes: http://mkncreations.com/files/images/taesports/infantryinput1.jpg (Auto resize: 265x868px, jpeg) 7. Just Below this section you'll find a similar section with the following header: ConceptYaw Again, find the appropriate block of data and make the following changes: http://mkncreations.com/files/images/taesports/infantryinput2.jpg (Auto resize: 265x868px, jpeg) 8. Save and close infantry.dbx Mouse Smoothing should be effectively disabled at this point. However this change will render turrets and vehicles nearly impossible to use, so make sure you follow the remaining steps... 9. In the input folder, open land.dbx using notepad 10. Search for the following line: ConceptPitch 11. Again, you'll see several similar-looking blocks of data below this section. Make the following changes: http://mkncreations.com/files/images/taesports/landinput1.jpg (Auto resize: 265x868px, jpeg) Note: 10 here is a suggestion, again feel free to experiment. Values below 5 seemed too sluggish for my taste, while values far greater than 20 did not seem to make turrets any faster at turning, just more "squirrely" (changing directions more quickly, making it harder to stay on target). 12. Just Below this section you'll find a similar section with the following header: ConceptRoll Again, find the appropriate block of data and make the following changes: http://mkncreations.com/files/images/taesports/landinput2.jpg (Auto resize: 265x868px, jpeg) 13. Save and close land.dbx Note: The next section applies only to piloting Helicopters (not including the UAV). Gunner seats and the UAV seem to follow the "land" control guidelines for turning speed. Also this fix was only tested for mouse flight. If you fly with a joystick or keyboard-only controls, you'll probably have to play with these settings a bit more to get them to work with your setup. Good Luck! 14. In the input folder, open air.dbx using notepad 15. Same as before, search for the following line: ConceptPitch Below this line you'll see several similar-looking blocks of data. Make the following changes: http://mkncreations.com/files/images/taesports/airinput1.jpg (Auto resize: 265x868px, jpeg) 16. Search for the following line: ConceptRoll Again, find the appropriate block of data and make the following changes: http://mkncreations.com/files/images/taesports/airinput2.jpg (Auto resize: 265x868px, jpeg) Choppers seem to need much higher values to compensate for setting the "main" mouse sensitivity to zero in step 2. Much lower than 100 and the chopper is hard to move. I tried up to 300, and while it worked, it wasn't a significant change. Again, experiment and find a value that suits you. Like turrets, there is a hard-coded maximum turning speed that the game allows, so don't expect this to transform your chopper into a super stunt machine. 17. Save and close air.dbx 18. Start up BFBC2 19. ENJOY! 20. (optional)Curse EA as the servers go down again and go play single-player instead