I have been pondering this issue, as something about it seems wrong. I am leaning towards a rule from cyberpunk, where the amount of area you are trying to cover with fire would have an effect on what happens. If you are using a full-auto burst on a 5 meter wide area against a single target, it would have a way different effect then if you sprayed over a huge area at multpile targets. Perhaps an accuracy bonus reflecting the sheer amount of rounds going through such a small space (perhaps equal to the auto value of the weapon, which is decreased by one per additional target or additional 5meter area) or penalties to the people being shot at (to simulate the effect of being suppressed by a large volume of rounds). The rule as is just seem to be multiple attacks, and I feel that if damage is not to be calculated per bullet, and you can increase your damage by simply firing a burst, there should be some advantage to suppresive fire other then just multiple attacks.
Previous posts on this topic have said (and i heartilly agree) that automatic fire is HUGELY innacurate, but usually the idea of doing it is to, as said above, keep heads down so since there is no "panic" type of effect built in, I think penalty, again perhaps the auto factor of the weapon, would be reasonable.