The real issue in regards to this tragic event is how to revoke or suspend the second amendment rights of an American citizen suspected of having ties to known terrorists or espousing terrorist ideologies.
I understand the shock and rage at guns, but to be blunt "ban all guns!" isn't going to happen and to me is just as stupid as morons going out in the next few days and buying up as much guns and ammo as they can because they fear Emperor Obama will finally execute his executive order.
That being said I've said time and time again that each individual state will need to decide for themselves how to want to deal with it. Being Florida, honestly, I don't expect anything to change. But let's not pretend there are not states that didn't at least TRY (as poor as some of their specific policies were and as common sense as other specific policies were) to adapt their gun laws to a 21st Century w/ 2A. NY, CT, CA are examples.
That being said debating the efficiency of the rifle is mostly irrelevant to me as he could have killed as many people with a wide variety of different gun types. The key should be how to keep someone on a terror watchlist from possessing and purchasing a firearm.
I think a layer of due process should be added to those "watch-lists" this way it can be perfectly legal to block someone on a terror watchlist from obtaining a firearm.
The only way the Second Amendment goes away is once it's relegated to irrelevancy due to non-use. One could make the argument that is exactly what's happening now as less people are purchasing firearms (although they do purchase more of them). It's easy to see a time (not in out lifetime) where no one will really push back against such an endeavor since no one is really owning guns like that.
I don't agree with it, but that could be one direction the current trend leads to.