(maybe I shouldn't have said this)
Eh, some of you or maybe large number of you already knows for this (don't consider me an idiot), but for those who not let them know:
I did some searching of sounds and I downloaded a sound mod for MOHAA. Inside of .rar archive there was a file with an extension .pk3. As usually I've extracted it but it served me for nothing, and then I tried to open it inside of archive - and it opened the file! There were folders with weapon sounds - just what we need. I did a research and read that those kind of files use games based on quake 3 engine and that they're just .zip files with renamed extension. Knowing this you're able to get more then just weapon sounds of course. Take them from games, or find them in internet archives. Here's my resource:
http://medalofhonor.filefront.com/files/Medal_of_Honor/Mods/Sound_and_Music;1244
