Check with your state, but in Idaho, all our laws say regarding full auto weapons is "As far as we're concerned, it's just another gun. just don't do anything that'll piss off the damn feds." So if you own it legally, you can CC or OC it in Idaho, as I understand. (though in a self-defense scenario, bear in mind that its usually a bad idea to whip out your Mac11 and start spraying .380 slugs all over the place when there are bystanders around. go with hollowpoints and short, controlled bursts.)
As far as having your gun discharge... like, what do you mean? Are you asking "what if my gun just goes off all by itself?" ...That doesn't happen. Unless you're using nitroglycerine instead of gunpowder and you slip and fall on some ice or something.