Yo Vilic;Guns & other weapon loadouts are controlled by entries in the aircraft .dp file. (
damage
profile)
No .dp file - No weapons

... simple eh?
- this also applies to any CFS2 object that is destroyable.
The .dp file is fairly easy to modify IF you understand the entries listed in it.
To be able to read & understand these I direct you the "Caleb Klerk's" site.
http://www.cfgse.calebflerk.com/cfgsedownload.htmLook under the "Downloads Tab" .. there you will find a number of tutorials in e-book (.exe) format.
There are many e-books covering all aspects of sim aircraft.
The best being the: .dp guide ( cfgse_DP.exe )
This will fully explain each entry in the gunstation code plus offers a wealth of info on modifying the .dp
Everything is free to download & use.
For FS2004 planes; first you'll need to convert them to operate in CFS2.
Good Luck Bro ....
Have a Blast!!! 
;D ;D
- Dirt