I will use semi if its an incredibly easy shot, or if I am trying to be more stealthy. Like if I find myself behind the opposing team, I would down whoever I could with a semi. That way I cold save ammo and I would make less noise. But overall I think full auto is the way to go.

Unfortunately, the people I play with wear so much gear, you have to really drill them in order to make sure they feel it. lol