hi mpgh for the people using Rapid fire and crashing its simple
just change your default combat arms fire key to some thing other than left mouse click.
Reason behind the crash is that the code it's self is bind the left mouse button "fire key".
Now with you pressing the left mouse key as well it's sending twice as many fire packets to the server which causes the game crash.
now if u change the default fire key you guys should'nt have any trouble using Rapidfire
here is a screen shot for noobs