Sorry to break your balls Conan, but you brought up all the most common arguments. So...
I really don’t see the issue with the high capacity weapons.
Lets start with the fact that weapons like the AR-15, and variants thereof, were developed with a single purpose in mind: the ability to shoot at people rapidly, accurately, with little recoil and minimal need to stop and reload. If you had to pick a weapon to hand to someone to shoot as many people as possible as quickly as possible you would pick an AR or an AK. That's why all the militaries of the world and many most armed police forces use them.
These weapons were developed, and are the pinnacle of design for the purpose of having one person shoot others.
Where we see many of these shootings happen are places where it is expected the people inside will be un-armed like schools, public buildings, theaters, night clubs, etc. Places where it is either illegal to carry on premises (I’m assuming it was illegal to carry in a bar in Florida like it is in Oklahoma) or are posted as no weapon areas.
So the solution is to encourage drunk people to carry weapons? To encourage people to carry weapons at schools? To encourage people to bring firearms to stadiums, political rallies, and hospitals? Because the US military over a couple hundred years of experience has determined that the average solider cannot be trusted with a weapon on base, but we are going to trust Joe Citizen with a weapon in a stadium after a few beers?
We would have better luck creating deterrents in public places with an armed guard or loosening restrictions on where people can conceal carry.
If there is no armed resistance inside it matters very little what gun the killer is using. With no armed resistance he/she is free to reload and shoot all they want unless the gun jams. Granted, a single shot Derringer would be very impractical, but you could get away with using a wheel gun or single stack semi auto like a 1911.
In several of the mass shooting incidents there were armed guards present or quickly on the scene. They were not effective. (Ft. Hood, Gabby Giffords. At Columbine police where there in 2-3 minutes. Etc.). If I can fire 100 rounds in 1 minutes, certainly I can spare one to shoot the guard first. Also - you can't deter a suicide mission by threat of return violence. So not only is requiring armed guards likely to be ineffective, but it is also economically disastrous. An extra employee for every business, whose job doesn't involve contributing economically to the business. Ouch.
Here's the cold hard facts: the United States of America has more firearms anywhere else. We have more people carrying firearms than anywhere else. The number of firearms being sold & carried has been increasing. Yet all of these facts are strongly correlated with mass shootings... if more firearms made us safer, wouldn't we be the safest country in the world?
Rather we are an outlier for gun violence. If guns made us safer...
The other issue is, gun restrictions have not proven to prevent mass killings. Sawed-off shotguns are illegal, yet they were used at Columbine along with a TEK 9 and another long gun. I’m not sure if the TEK 9 was even legal at the time under the Clinton gun ban. The semi-auto rifle used in Sandy Hook was illegal to own or possess there.
What I’m getting at is you can pass all the bans you want, that doesn’t clean out all the gun safes and closets where these weapons already exist.
First, I need to point out that the gun lobby is so afraid that data doesn't support their position that they have very effectively lobbied for a ban on anyone studying the topic. So while "there is no evidence..." may be a somewhat true statement, its also rigged. When you ban funding for anyone to look for evidence or a solution to a problem, it makes sense that you are not going to find evidence or a solution to a problem.
Second, at Columbine, 2 murders with careful planning and an arsenal of weapons killed 12 people before police got there 2 or 3 minutes later. Most of the damages was done with a TEC-9 with clips of various sizes, all about 25 rounds (including a 52 round clip). The murders used an 18 year old girlfriend to buy the weapons for them, but it appears they would have all been legal gun-show purchases in Colorado anyway. While they had other weapons, the spray and pray shooting in the cafeteria with the Tech 9 high capacity magazine was the most deadly. Second to that was the Highpoint 9mm "carbine" with 10 round clips.
Finally, we can keep saying "there is nothing we can do, there's too many guns!" Then we go back to encouraging everyone to buy more guns. We've done that for decades and decades. We've made carrying firearms easier. We've made assault weapons easier to get. And it certainly has not had the desired effect. Everywhere else that has enacted gun control has seen the desired result... but we pretend it just won't work.
I mean, other than the fact it HAS worked when we've done it in the USA. In the 1920s we had a problem with mass shootings in the USA. The mafia and bandits would buy a Thompson from Sears Roebuck and do as they please. The Federal Government saw fit to require citizens to take extra steps if they wanted a machine gun. Now, even though there were plenty of them around at the time - eventually the number of shootings involving machine guns started to drop. Within a generation they became rare. Now, they are unheard of in the United States. (1934 put the first restrictions in place, a 1986 law stopped new sales to citizens).
Now you're thinking I've gone off the rocker and need to turn in my weapons. But wait, there's more! I don't want to take your gun away any more than I want the government to take my firearms away. But lets start with two acknowledgments from both sides:
1. There IS a problem with firearm violence.
2. We DO have an individual right to have firearms.
Then I have one proposal:
3. Lets start with removing funding restrictions on trying to find solutions to the problem.
Then we can try to balance my right to own a firearm with my friend's right to not be shot at school/church/nightclub/work. We did a really good job with machine guns. We do a pretty good job with conceal carry holders right now (few murders are accomplished by license carry holders).
Will we solve the problem in a month, or even a presidential term? Nope. Will we stop all gun violence? Hell no. But within a generation I'm sure we can come up with solutions that allow law abiding, competent, and sane citizens to own assault rifles, but do a better job of preventing people with a desire to connect with terrorists, mental instability, or who want to murder people from owning a weapon that makes mass shootings into something just about any moron can do.
But in the current climate, we can't even have that conversation. This isn't a call for gun control. While I can respect the commitment of the Democrats sitting on the floor right now, legislating in a climate of "crisis" is almost always a bad idea. Both sides need to calm down, have a conversation without regard for the NRA or for the parents of victims, and realize that we can do better.