[HELP] M9 Hex modding

What am I supposed to search for when I'm trying to hex mod the ROF of a m9.
I have used the search button on many sites and they just kind of keep the secret on the low low.

I know to search for fire but I don't know what to edit in there I know its FIRE_KEY but what do I edit from there :P I'm gona do a 00 and 01 mod so...