Man I don't know what build y'all are using. I can put my squaddies on RF and they do it, I think. I don't actually remember, with the AI as static as it is, I don't need RF very often. But I can set every small arm to it, but not the MG or Rocket Launcher.
But seriously the point of an MG is that it weighs a crapton, but gives in proportion. They're too heavy and the ammo is too hard to carry for everybody to have one, but the act of firing it isn't any different from the rifle.
If it's too self sufficient, just up the weight a little and double the size of the ammo boxes (to 2x2) so that they take up a lot of room in the gunner's inventory. Maybe up the weight of the ammo too.
It just feels weird knowing that if I don't leave somebody to babysit him, anything can come around a corner and whack him. That makes perfect sense for the bazooka (it's hard to aim, and you don't want to waste the rounds), but a machine gun is just a really big assault rifle.
Unrelatedly - does the medkit do anything yet?