All of what you read below applies to every Battlefield game on PC from BF4 until the present day, including my own personal settings, summarized at the bottom of this sheet.
This guide existed for BF2042 in it's launch state and up until April 2022, with Update #4.0. Prior to that update, you had to finely adjust sensitivity in PROFSAVE_profile. After the update, the ability to edit sensitvity by decimal points was brought back from the dead (and BFV). Along with this was a general fix for the underpinnings of how mouselook works in 2042, reverted to the system used since BF4. This allows this guide to be relevant to multiple BF titles.
If you wish to more finely tune your sensitivity, keep reading.
Navigate to:
BF4:
Documents\Battlefield 4\settings\PROFSAVE_profile
BF1:
Documents\Battlefield 1\settings\PROFSAVE_profile_synced
BFV:
Documents\Battlefield V\settings\PROFSAVE_profile_synced
BF2042:
Documents\Battlefield 2042\settings\PROFSAVE_profile
and open the file in a text editor of your choosing.
Next:
Ctrl+F search for GstInput.MouseSensitivity
And the fun bits:
Each time you increase the sensitivity in game by 1, the long decimal number next to GstInput.MouseSensitivity increases by 0.001500 with a minimum of 0.000000 and a maximum of 0.015000, which correspond to 0 and 100 in the game menu, respectively. If you set the game menu to 5, the decimal will show 0.007500. Simply multiply the game menu value by 0.001500 with a calculator to find the decimal value you wish to start with.
To dial in the sensitivity in finer points, the game menu allows adjustment in 0.1 ticks or tenths of a tick, or 0.000150 in the settings file. This is done by selecting the sensitivity slider and then using left and right arrow keys. This should be perfecly fine for the vast majority of players, even 80%-85% of Snipers, as adjusting less than one tenth of a tick is barely able to be felt by all but the most finely aware players. To adjust even more finely than this, I would suggest shifting by 0.000010 at the least, anything less is peanuts and you won't notice much. If that is too little, adjust by 0.000075, or twentieths (1/20) of a tick. Overall, update #4.0 brought this game's sensitivity settings almost perfectly in line with those of Battlefield V.
This is the math I originally used to finely adjust my sensitivity prior to PC sensitivity being reverted to the prior system before BF2042 Update 4.0
I started by adjusting in quarters of a tick (a tick being one number in the game menu). One quarter tick is 0.000375. Dividing further causes an extra decimal place to be added, and as the game only reads out to six decimals, anything past that will cause the sixth to be rounded up or down. One eighth tick is 0.0001875 and because the seventh place is 5 or above, it will round up to 0.000188. To adjust more finely than quarters, I suggest adding or subtracting 0.000010 from the quarter value you have found. For instance, if you have found 0.004375, or three and a quarter (3.25) to be nearly perfect, make it 0.004365 if you feel like going a little slower.
All of the above also goes for the vehicle sensitivity, which can be found the next line down in the file as GstInput.MouseSensitivityVehicle.
This is 100% optional, but it is nice. In essence, based on your aspect ratio, this will even out sensitivity across optic zoom in game. Older games like CS:GO have something of similar or identical operation, but locked to the coefficient for 4:3 displays, as that is what most players are used to for this system. Battlefield is one of the few games that allows you to alter this.
If using a 16:9 display, set the coefficient to 177.7% in game, but if you want it finer, go to:
BF4:
Documents\Battlefield 4\settings\PROFSAVE_profile
BF1:
Documents\Battlefield 1\settings\PROFSAVE_profile_synced
BFV:
Documents\Battlefield V\settings\PROFSAVE_profile_synced
BF2042:
Documents\Battlefield 2042\settings\PROFSAVE_profile
and find GstInput.UniformSoldierAimingCoefficient and set its value to 1.777777.
For 4:3, set the coefficent to 133.3% in game, or 1.333333.
For 21:9 Ultrawide, set the coefficient to 233.3% in game or 2.333333.
For 32:9 Ultrawide, set the coefficient to 355.5% in game or 3.555555.
Every time you adjust the sensitivity in the PROFSAVE_profile file, you will have to save the file and restart the game to see the effects. DO NOT open the settings menu during this process as it will cause your sensitivity value to be reverted to whatever it was when you last started the game.
The mouse currently in use will be at the top of this section of my PC setup sheet, also here on Gist.
Currently, after Update #4.0, Game Version 0.4.0 (April 19 2022), I use the following:
Vertial FOV: 91.5 (most games use horizontal FOV, this is roughly 122 horizontal FOV)
Mouse DPI/CPI: 1600
DPI Deviation as explained and investigated by Ali at Optimum Tech
For mice with no discernible DPI deviation, I default to an in-game sensitivity of 0.00750 or 0.5 tick. This is the most "pure" respresentation of my game sens as everything is on target. After switching to glass mouse feet, I use a sensitivity of 0.000300 or 0.2 tick. Previously, I used an in game sens of 0.004500 or 2.5 ticks. Every mouse deviates a bit, even within the same model, so adjust how you need to to aim your best for your playstyle!
Prior to Update #4.0, I used a sensitivity of 0.004688 or about 3.125 ticks, 3 and 1/8ths ticks.