It is a common argument. "Why does anyone need 30 rounds?" That is a question asked by someone who doesn't understand firearms used for a lawful purpose. Unfortunately, the common response I hear and read from gun owners is "Because it's my right". That is not a compelling argument, especially not for people who question the validity of the 2nd Amendment. Let me humbly suggest this tact. For spree shooters, the number of rounds is irrelevant. Assuming their weapon of choice is a gun, which is not always the case, spree killers are not hampered by reloading. Their victims cannot shoot back and the ability to rush the killer when they are reloading is not as easy as it sounds. Granted, single shot weapons might help reduce the carnage but two very prolific shootings happened during the previous "Assault Weapons Ban" that limited magazine capacity to 10 rounds (Columbine and Virginia Tech). The Clocktower Shootings in Austin, TX were committed with no weapons that held more than 10 rounds. A determined killer will always find tools of mayhem regardless of the law. However, for self defense purposes, capacity matters. Shootings in real life do not happen like Hollywood. Self defense can take place with one person against multiple assailants. Reloading may not be an option or seriously increase risk. Limiting ammunition capacity would not have made a difference in any of the shootings we've had recently, but it could potentially cost the life of someone using a firearm for lawful self defense. If you live in a rural area, you may be on your own for a quarter of an hour or more. A lot of gun control advocates think only urban. Someone armed with an AR-15 and 30 round magazines might be the only defense they have for their land and property. A short range handgun or shotgun may not cut it. If you are defending yourself at medium to long range against multiple assailants, does it make sense to limit your magazine to 10 rounds? The counter to this is "Those situations are rare", and that is true. But they are actually more common than spree killers, and that is including killings done without firearms. Spree killers are actually relatively rare compared to defensive gun uses. They are just incredibly sensationalized by the media. We're going to take a tiny percentage of criminal activity and put lawful citizens at risk? We're going to further reduce people's ability to defend themselves as an answer? Now, some of the knowledgeable people of this forum will counter with "I carry a J-Frame..." That's your choice and what we're talking about here is choice. If someone feels they need a Glock 19 for self defense and live in a bad area, that should be their choice. They should not be forced to limit their Glock 19 to 10 shots before a reload. That is potentially fatal. You hope that no one needs that many rounds if they do actually have to shoot, but no one ever complains about too many bullets in a gunfight.