We have all heard rockwell's rant about how firing full auto or supresive fire over an entire combat turn should take more than 10 bullets. yada yada. here is my sugestion.
SR4 says a combat turn is ~3 seconds, lets just streach that to 4 to make math easy.
Each combat turn has 4 passes- 1 pass=1 second
At full auto a gun would fire 10 rounds a second and have a firing rate of 600 rounds per minute. (actually kinda low compared to real life counterparts.)
When shooting full auto at a target, if you have no more passes that turn you may continue to fire full auto. Make a second test with an aditonal -10 recoil penalty (usualy this would make taking this option pointless) if you are reduced to bellow 0 dice you would have to make an edge test or roll 1d6 to keep from glitching out. haven't thought that through a whole lot.
This creates a situation where some one can fire at a target full auto for an extended amount of time. but if they don't have multiple inititive passes they have to pause to be able to comp for the recoil. follow me?
I suggest a similar system with suppressive fire. More bullets spent but it has the additional bonus of forcing a dodge test every initiative pass, not just when you have an action.
I can't find the post that I made before about altering the shadow run combat turn slightly. at least the interpretation of it. I'll link it if i ever find it, but I belive these rules fit in well with the concept of having multiple IP lets you act in X number of passes durring a combat turn, and you may want to wait until a later pass to act.