It seems to me that the AI behave the same with bolt-action or semi-auto. Personally I would think it might be more interesting to differentiate their behavior with a semi-auto by making them either fire in a somewhat faster rate or to immediately follow up another 2~5 extra shots in fairly rapid succession after their first carefully aimed shots with the following fire being less accurate of course.
This would make the sounds of firing a bit more distinct so that you can tell what is used by the rate and spacing of shots being fired from other soldiers and potentially give some more incentive to arming AI with semi-auto weapons aside from using the standard bolt action.
