Gorlom you math is correct.
I started reading the suppression mechanics threads and was thinking of adding my 2 cents, but the thread so long I read some of it. So excuse me is what I'm suggesting is already been covered. Suppression fire is as much reactive as it is proactive, and assault rifles are capable of suppression fire as well as machine guns. Three shot burst on a assault rifle is for suppression fire in game that could translate into single shot being higher damage low suppression, while burst fire high suppression lower damage. Machine guns with controlled bursts would be lower suppression higher damage while full auto would be high suppression lower damage. As far as the suppression fire goes I also think there should be a suppression mode for reactions. Basically if a soldier is intended on doing suppression fire as a reaction to an alien(or vice versa) poking his head from cover or concealment a mode should she be toggled. Reaction shots while in the mode would be at a reduced AP and a reduced accuracy to balance each other and to throw more bullets down range. This would help to give the feel of suppression fire.