Yeah you are totally right, the Warthog should have a different sound for when it hits the armor... We completely forgot to fix that!
EDIT: Just fixed that. We had the sound ready to go, just forgot to add a line in a script.
Wow, really glad to hear that! Thanks for playing! it's comments like these that make it easy to love making games. =D
If you're interested in making stuff, definitely go for it!