[COD4] does anyone know what im doing wrong?

im replaying the game on a ps3 and for some reason it refuses to count the squadron record both the dialogue and the achievements dont aknowledge it at all even though ive had a time below 19 seconds for 5 times i tried looking it up and the only thing i found was a guy saying you have to use the mp5 but that didnt help either i had no problem getting this achievment on a xbox 360