Well, the way I've decided to do my automatic firing, is that each weapon has a singleshot mode, and a fully-automatic mode (some weapons are just one or the other) and it has a different UR for which rate of fire you want to use. The basic assault rifle my army uses, the VX-5, can fire one shot with a UR of 3, or two shots with a UR of 4. The more powerful version, the MA-3, can fire one shot with a UR of 4, or three shots with a UR of 5. My heavy machinegun, the ME-23, only fires fully auto, and fires a total of 16 shots per firing, with a UR of 6. The BK-8 Battlerifle (based on the Battlerifle from Halo 2) is also only fully-auto, and fires three shots at a UR of 5.
So yeah, those are just examples of how I play with automatic fire. As far as I'm concerned, having set URs and set numbers of bullets makes it easier since you don't have to spend time figuring out the UR and how many bullets you want to fire and stuff like that.
"For every battle honour, a thousand heros die alone, unsung and unremembered"
"Glory to the first man to die!"
"When in doubt, empty the magazine!"
--Steel Legion motto