OK, a fair while ago I posted this info regards changing weapons loadouts using 'Notepad' (or Wordpad) to add the custom loadouts directly into campaign and mission files without using Full Mission Builder for anyone not familiar with using it. This sounds complicated but is quite simple. I have placed a example single mission in the next post that you can copy/paste to try a diferent loadout to the stock one. Instructions are at the beginning.
http://forum.1cpublishing.eu/showthread.php?t=21773
First, User loadouts are stored in a User.Ini file under what ever name you saved them and for each ac that you create a custom loadout. The User.Ini should be found in the 1C game folder and the Steam Folder but for some odd reason not always.
The Loadouts themselves are created in each planes weapons options menu - it is here that you select the ordinance for each gun and set your convergence then name and save your loadout.
Once you have done that, open the User.ini file with notepad and you should see your weapons loadout associated with the ac.
Have a read of the thread I linked - you can copy the sample loadouts in the thread by highlighting the text - Ctrl C to copy the text into your PC's memory then Paste Ctrl-V directly into the mission file the sample does not use the De Wilde - just add code 11 in each of the eight guns -----that will sort the hun out!
All the Mission files are stored with the extension .MIS in the mission folder of the game directory and these are just simple text files that you can also open with Notepad and edit - once again some are in 1C and others in Steam Directory.
The thread shows sample loadouts and how to simply paste your weapons loadouts from the user.ini file directly into the mission file. You can even create your loadouts using notepad directly into the user.ini file
Do a search for Weapons loadouts -there are plenty of threads.