Me: I think we should firearms with removable magazines to be regulated the same as a machine gun. The 1934 National Firearms Act regulates machines guns and certain other types of weapons. Civilians can purchase a machine gun, but the person must submit a photograph and fingerprints for a background check, must get the approval of the local police chief, must pay a $200 transfer tax, and must provide the serial number, etc, to register the weapon. Since the NFA regulated machines in 1934, only 2 legally owned machine guns have been used in homicides. Regulating firearms with removable magazines in a similar manner would still allow law abiding citizens to have assault rifles, would help reduce crimes committed with such weapons as the flow of assault rifles becomes regulated making it harder for legally owned guns to end up in the hands of criminals. The cost benefit analysis would look like this:

Me: Firearms with removable magazines would be reclassified the same as machine guns. Hunters mostly use non-removable magazines, therefore they would be unaffected. People who want a handgun for self defense can use a revolver. If you really, really have to have a firearm with a removable magazine, then you can get a Class 3 Federal Firearms License and get the weapon you really, really, have to have.
Them: But guns should be freely available.
Me: There are more than 100,000 machine guns legally owned by civilians right now. How much more freely available do you need?
Them: But why would you want to regulate all semi-automatic weapons as if they were machine guns?
Me: Not all semi automatic weapons, just weapons with removable magazines. Revolvers and long guns with fixed, non-removable magazines (most hunting rifles and shotguns) wouldn’t be affected.
Them: But having a removable magazine isn’t the same as being a machine gun.
Me: Meh. The US M16 rifle has been the standard miltary issue for the last 50 years. During the Vietnam war, the standard issue magazine was 20 rounds. The magazine was later expanded to 40 rounds. Early versions of the M16 were full auto. Later versions didn’t have full-auto and instead only supported a 3-round burst mode. So, even the US military acknowledges by design that the killing capacity of their standard issue infantry weapon doesn’t come from being fully automatic, but rather from having large capacity, quickly reloadable, magazines.
Them: Getting firearms with removable magazines out of the hands of psychopaths won’t change anything.
Me: It would have changed the 2011 Tuscon shooting, Jared Lee Loughner had a Glock with a 33 round magazine. Loughner killed 6 and wounded 13 people, and then he stopped to reload, and was tackled and disarmed. If he only had access to a 6 shot revolver, which is also harder to reload, then he could have been stopped earlier.
Them: But if someone in the crowd had a gun, they could have shot Loughner and stopped him.
Me: According to reports, Joe Zamudio was armed and in a nearby coffee shop when the shooting started. He came out, grabbed a man with a pistol, threw him against the wall, and was close to shooting him, when he realized he had the wrong guy. Loughner had already been tackled and someone took the gun away from him. That was who Zamudio threw against the wall.
Them: But if someone had been closer, they might have been able to stop Loughner.
Me: Yes, and they could do that with a revolver.
Them: But they might need more than 6 shots!
Me: That means this person fired 20 or 30 rounds into a crowd at Loughner and missed. Not exactly an improvement of the situation.
Them: You’re not taking everything into account. The second ammendment says my right to keep and bear arms shall not be infringed.
Me: It says “A well regulated militia being necessary to the security of a free state….” You completely ignore the part that says REGULATED.
Them: I need to be able to defend myself against future, possible, hypothetical tyranny from my own government, and I need to be able to resist that tyranny by having the firepower to launch an armed insurrection against my own government. The cost/benefit analysis should look like this:

Me: uhm….
Them: Clearly the scale tips in favor of no regulation of guns.
Me: So… right now, 10,000 people are murdered every year by guns. People are killed in mass shootings on a regular basis. How many people would have to die before you’d be willing to consider regulating weapons with removable magazines?
Them: You don’t understand the power of my paranoia. It doesn’t matter how many real people die every year from real guns, my paranoid delusions can always manufacture an even more terrible worse-case scenario where the American government sends in the military and kills even more poeople than are murdered by your criminals.
Me: So, if 50,000 people were murdered by guns every year?
Them: That would still be outweighed by my theoretical, hypothetical, paranoid delusion involving the US government sending the military into New York city and killing everyone who lives there. That would be a hypothetical, theoretical, death toll of millions. How can the real deaths of a few thousand outweigh the theoretical, hypothetical deaths of millions of people?
Me: Why would the government even do that?
Them: That doesn’t matter. What matters is I can imagine it, therefore the second ammendment says I am allowed to defend against it.
Me: I’m pretty sure the second ammendment doesnt work that way.
Them: Nuh huh! It totally does. If I can imagine a scenario of government totalitarianism, and the only way to resist that is that I have a fifty caliber, belt-fed, machine gun, then the second ammendment says I get to have a fifty-caliber, belt-fed, machine gun.
Me: Well, you can have a fifty-caliber, belt-fed, machine gun right now if you file paperwork with the BATF. You can find machine guns for sale on Google, for cripes sake. I’m just shifting some weapons into the same category as machine guns. They’re not outlawed. They just require more paperwork.
Them: No, see, my worst case, hypothetical, paranoid delusion, also includes the sub-plot that registering guns is the governments first step in figuring out who goes into the gas chambers first. In fact, any attempt to regulate guns only reinforces my belief that my paranoid delusions are coming true. Why else would you want to regulate guns but to know where I live so you can round me up and put me in a gas chamber?
Me: Because 10,000 real people are murdered every year by guns and regulations can reduce that death toll?
Them: Bah! That’s one place where your math is wrong. Clearly a million potential hypothetical deaths generated from my paranoid delusions are more important than 10,000 real murders every year. Another place your math is wrong is thinking that getting assault rifles out of the hands of psychopaths would make any difference whatsoever. Psychopaths would just get a sack full of revolvers. And they would create just as much carnage.
Me: Wait. If a sackful of revolvers is just as deadly as an AR15, then why not let us regulate weapons like AR15′s and you could buy yourself a sackful of revolvers. If they’re exactly the same, you should be able to resist tyranny with a sackful of revolvers as easily as an AR15.
Them: …
Me: Unless you know an AR15 is more deadly than a sackful of revolvers, but now you’re just lying to try and get your way.
Them: …. Fuck.