I don't see a FA either...but, there are those who claim not to need one..
I, on the other hand, know nothing but (well, I did have an original AR-15 w/o one) but I've got a bajillion more hours on the M16A1 and M4A1 that had one, so I wouldn't feel comfortable w/o it. (all my BM's have FA) (YMMV)