I just measured it now to be sure, and it is definitely a 16:9 FOV. Remember that the hipfire sensitivity is affected by the Monitor Distance Coefficient, so make sure these settings are the same in the calculator and in-game.
https://support.microsoft.com/en-us/windows/show-hidden-files-0320fe58-0117-fd59-6851-9b7f9840fdb2#:~:text=Select the Start,then select OK.
Then press win+r type %LOCALAPPDATA%\HLL\Saved\Config\WindowsNoEditor