Chris Cox is executive director of the National Rifle Association's Institute for Legislative Action

Since the senseless January 8 attack on Arizona Rep. Gabrielle Giffords and her innocent constituents, NRA members have joined our fellow Americans in offering thoughts and prayers for the victims, for their families, and for the Tucson community.

Yet while we grieved, anti-Second Amendment groups worked to exploit the tragedy to resurrect their political agendas. "In the wake of these kind of incidents, the trick is to move quickly," one antigun activist said.

High on their wish list is banning ammunition magazines capable of holding more than 10 rounds. This failed ban was in effect from 1994 to 2004; bills in Congress would bring it back and make it even more restrictive on honest citizens. These magazines are standard equipment for handguns and other firearms owned by tens of millions of Americans, just as they were before and during the earlier ban. Besides using them for self-defense, gun owners own them for competitive or recreational shooting, as key parts of collectible firearms, and for other lawful purposes.

In a letter to her colleagues, New York Rep. Carolyn McCarthy made the claim (echoed in countless newspaper editorials) that "The only purpose for the existence of these devices is to be able to shoot as many people as possible as quickly as possible." Yet even her bill would allow law enforcement officers—who obviously carry guns to protect themselves and the public, not for mass murder—to continue to acquire and possess these magazines. The bill would also allow magazines to be transferred to police officers upon retirement, even though a retired officer's right to use firearms for self-defense is the same as any other private citizen's. [Read the U.S. News debate on "open carry" gun laws.]

Why do honest Americans—private citizens and police alike—choose magazines that hold more than 10 rounds? Quite simply, they improve good people's odds in defensive situations. Contrary to what the public sees in the movies, criminals are not always stopped when struck by a single bullet, or even multiple shots. And one third of aggravated assaults and robberies involve more than one assailant, according to the Justice Department's Bureau of Justice Statistics.

Ask yourself: How many rounds would you want to have on hand if you knew you were going to be attacked tomorrow, but didn't know how many attackers you'd face, whether they might be on drugs, or whether you'd have time to reload? [Take the U.S. News poll: Should more Congressman carry guns for protection?]

The earlier ban was proven a failure. A congressionally mandated study released in March 1997 found that the banned weapons and magazines "were never involved in more than a modest fraction of all gun murders." The study also "failed to produce any evidence that the ban reduced the number of victims per gun homicide incident" and found that "the average number of gunshot wounds per victim [about two] did not decrease" after the ban.

Since the ban expired in 2004, the nation's murder rate has dropped 10 percent, continuing a long-term decline that began in 1991. Through 2009, the murder rate is at a 45-year low, and the FBI recently reported that it fell an additional 7 percent in the first half of 2010. Mayor Nutter's city, unfortunately, has lagged far behind the rest of America, with a murder rate that returned to early '90s levels in recent years. While Philadelphia politicians call for gun control, nearly two thirds of violent-crime defendants in Philadelphia over a recent three-year period avoided conviction. [Read more about gun control and gun rights.]

Antigun activists ask, "Who needs these magazines?" Good Americans—police and private citizens—do. Good Americans must always be able to choose the tools that will give them the best chance of surviving in the worst situations.

Read Philadelphia Mayor Michael Nutter on why high-volume ammo clips should be banned.

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