The question that you have never answered honestly: why would a mass murderer use an AR-15 as his weapon of choice?
The few mass murderers who are dumb enough to choose the AR-15 as their weapon of choice to kill large numbers of civilians do so for theatrical purposes. They generally admire other mass murderers who did the same, and they equate the look and media reputation of the AR-15 to personal power. They use an AR-15 because it subjectively makes them feel powerful, and they are either willing to sacrifice lethality for this, or are blessedly dumb enough to not understand what makes a firearm effective in a mass shooting scenario. Or else they are resigned to suicide and don't care about being immediately shot by police or an armed bystander.
Concealable handguns and spare magazines loaded with hollow point ammunition are tactically way more efficient weapons to kill large numbers of civilians in an enclosed area than AR-15's are for a large number of reasons. In fact, the only real advantages AR-15's and other sporting rifles would have over handguns in a mass shooting scenario is better accuracy at longer range, (which is completely lost in close range rapid fire scenarios, which are the majority of mass shootings,) and armor piercing capability, (an added concern only for law enforcement officers who are rarely the targets of mass shooters. A civilian isn't going to experience any difference between getting shot with an AR-15 or a 9mm.)
Magazine capacity is a wash because, while AR-15 magazines hold more rounds, the magazines themselves are much bigger and heavier, so fewer can be carried on the person, and it is harder to conceal them.
Damage to soft targets is a wash, because at point blank range, (the most common range that mass shootings happen) an AR-15 round is more likely to pass completely through a soft target making a smaller hole and doing far less damage than the larger, slower pistol round. At close range against a soft target like a civilian, a pistol round is no less deadly than an AR-15 round, and is quite often more deadly. Unless you are shooting at longer ranges from a concealed position, handguns make more sense. And other rifles besides AR-15's make more sense if you
are shooting long distance from a concealed position. Most hunting rifles have more lethality and accuracy at longer ranges than AR-15's do.
Concealability is where the real advantage lies when it comes to mass shootings. A man with an AR-15 is an obvious target as the Greenwood Park Mall shooting proves. A man with a handgun could kill 18 people as fast as he can pull the trigger, and either surreptitiously reload and continue multiple times, or holster the weapon and join the fleeing victims to get away.
There is no tactical advantage to using an AR-15 or any other sporting rifle in a civilian mass shooting scenario. It is an ego move and nothing else.
publichealth.jhu.edu
www.pewresearch.org
