From the Wall Street Journal, January 19, 2013.

Mr. Lott's analysis shows the foolishness of Obama's, Feinstein's and the media's focus on guns as the problem and their desire to regulate them or eliminate them from public ownership if they could. The problem, so much more difficult to solve, is the identification and control of the crazies that perpetrate these heinous slaughters using guns. Guns aren't the problem; people are.

Facts have been subjugated in favor of political rhetoric.

By JOHN R. LOTT JR.

Warning about "weapons designed for the theater of war," President Obama on Wednesday called for immediate action on a new Federal Assault Weapons Ban. He said that "more of our fellow Americans might still be alive" if the original assault weapons ban, passed in 1994, had not expired in 2004. Last month, in the wake of the horrific shooting at Sandy Hook Elementary in Newtown, Conn., Sen. Dianne Feinstein (D., Calif.) promised to introduce an updated version of the ban. She too warned of the threat posed by "military weapons."

After the nightmare of Newtown, their concern is understandable. Yet despite being at the center of the gun-control debate for decades, neither President Obama nor Ms. Feinstein (the author of the 1994 legislation) seems to understand the leading research on the effects of the Federal Assault Weapons Ban. In addition, they continue to mislabel the weapons they seek to ban.

Ms. Feinstein points to two studies by criminology professors Chris Koper and Jeff Roth for the National Institute of Justice to back up her contention that the ban reduced crime. She claims that their first study in 1997 showed that the ban decreased "total gun murders." In fact, the authors wrote: "the evidence is not strong enough for us to conclude that there was any meaningful effect (i.e., that the effect was different from zero)."

Messrs. Koper and Roth suggested that after the ban had been in effect for more years it might be possible to find a benefit. Seven years later, in 2004, they published a follow-up study for the National Institute of Justice with fellow criminologist Dan Woods that concluded, "we cannot clearly credit the ban with any of the nation's recent drop in gun violence. And, indeed, there has been no discernible reduction in the lethality and injuriousness of gun violence."

Moreover, none of the weapons banned under the 1994 legislation or the updated version are "military" weapons. The killer in Newtown used a Bushmaster .223. This weapon bears a cosmetic resemblance to the M-16, which has been used by the U.S. military since the Vietnam War. The call has frequently been made that there is "no reason" for such "military-style weapons" to be available to civilians.

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Sen. Dianne Feinstein

Yes, the Bushmaster and the AK-47 are "military-style weapons." But the key word is "style"—they are similar to military guns in their cosmetics, not in the way they operate. The guns covered by the original were not the fully automatic machine guns used by the military, but semiautomatic versions of those guns.

The civilian version of the Bushmaster uses essentially the same sorts of bullets as small game-hunting rifles, fires at the same rapidity (one bullet per pull of the trigger), and does the same damage. The civilian version of the AK-47 is similar, though it fires a much larger bullet—.30 inches in diameter, as opposed to the .223 inch rounds used by the Bushmaster. No self-respecting military in the world would use the civilian version of these guns.

A common question is: "Why do people need a semiautomatic Bushmaster to go out and kill deer?" The answer is simple: It is a hunting rifle. It has just been made to look like a military weapon.

But the point isn't to help hunters. Semiautomatic weapons also protect people and save lives. Single-shot rifles that require you to physically reload the gun may not do people a lot of good when they are facing multiple criminals or when their first shot misses or fails to stop an attacker.

Since the Federal Assault Weapons Ban expired in September 2004, murder and overall violent-crime rates have fallen. In 2003, the last full year before the law expired, the U.S. murder rate was 5.7 per 100,000 people, according to the Federal Bureau of Investigation's Uniform Crime Report. By 2011, the murder rate fell to 4.7 per 100,000 people. One should also bear in mind that just 2.6% of all murders are committed using any type of rifle.

The large-capacity ammunition magazines used by some of these killers are also misunderstood. The common perception that so-called "assault weapons" can hold larger magazines than hunting rifles is simply wrong. Any gun that can hold a magazine can hold one of any size. That is true for handguns as well as rifles. A magazine, which is basically a metal box with a spring, is trivially easy to make and virtually impossible to stop criminals from obtaining. The 1994 legislation banned magazines holding more than 10 bullets yet had no effect on crime rates.

Ms. Feinstein's new proposal also calls for gun registration, and the reasoning is straightforward: If a gun has been left at a crime scene and it was registered to the person who committed the crime, the registry will link the crime gun back to the criminal.

Nice logic, but in reality it hardly ever works that way. Guns are very rarely left behind at a crime scene. When they are, they're usually stolen or unregistered. Criminals are not stupid enough to leave behind guns that are registered to them. Even in the few cases where registered guns are left at crime scenes, it is usually because the criminal has been seriously injured or killed, so these crimes would have been solved even without registration.

Canada recently got rid of its costly "long-gun" registry for rifles in part because the Royal Canadian Mounted Police and the Chiefs of Police could not provide a single example in which tracing was of more than peripheral importance in solving a gun murder.

If we finally want to deal seriously with multiple-victim public shootings, it's time that we acknowledge a common feature of these attacks: With just a single exception, the attack in Tucson last year, every public shooting in the U.S. in which more than three people have been killed since at least 1950 has occurred in a place where citizens are not allowed to carry their own firearms. Had some citizens been armed, they might have been able to stop the killings before the police got to the scene. In the Newtown attack, it took police 20 minutes to arrive at the school after the first calls for help.

The Bushmaster, like any gun, is indeed very dangerous, but it is not a weapon "designed for the theater of war." Banning assault weapons will not make Americans safer.

Mr. Lott is a former chief economist at the United States Sentencing Commission and the author of "More Guns, Less Crime" (University of Chicago Press, third edition, 2010).