Nothing I've heard proposed would do a thing prevent mass murders like the one in Florida. It's just "feel good" bullshit. Even if you could prevent these psychos from getting a gun, they'd just use a car, uhaul truck, machette, sword, IED, or whatever other weapon they can get their hands on to do the deed. Securing the favorite targets like schools and churches would be much more effective, if the goal is to protect them. But we all know, the true goal of the gun control push is disarming the populous.
In my book, if you're old enough to give up your life in defense of your country, you're old enough to buy/own a gun. But then again I say the same thing about voting and buying alcohol.
