Thanks bat...I tried to modify each spit sound to reflect the different merlin variants. The spit 14 actually came from ReaAir's payware and is supposed to be real griffon recordings. I made the .303 and .50 sounds from actual recordings(not mine). Having heard them fired in real life, none in the game sounded anything like them and it bugged me.
You shouldn't need to register to download...it might have changed though.