Currently if you give ai an mp and a bolt action rifle they tend to switch to the bolt action rifle at some point, due to far away enemies and never swap back.
I think there should be some mechanic that lets them swap back, like swapping to it after a short while of no combat, like reloading or swapping to it after the first shot with a bolt action in cqc.
This is generally not that often a problem I think, due to it usually being better to not have bolt actions on assault soldiers at all, but for me there are a few exceptions like BR I germany, where you have not so amazing mps, but access to great bolt actions (especially if you have the old Kar 98k, which can be equipped to assault soldiers for some reason).