İ saw the 70 star wr and in that they mash very fast ist there a tech for this?

Yeah, you bind the fire input to mouse wheel up and down inputs and then just scroll really fast. It works best on mice that allow for unlocked scroll wheels that can spin with no resistance

How do you bind an input to a key

Either your keyboard and mouse software natively supports that kind of rebinding, or you can use an external tool to do that for you. For example, here's an AutoHotkey script that will do the rebinding for you: https://gist.github.com/lioncash/cdd12f360ca8a1b0f283b8d8eebf0cda (I'll also add this to the Resources tab for the future)

Oh i thought it was in game i didn’t know binding outside of the game was breaking the rules or not