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USA TODAY

A common thread links the mass slaughters of first-graders in Newtown, Conn., of county workers in San Bernardino, Calif., and of nightclub patrons in Orlando: The killers used assault-style weapons that are efficient machines of murder.

Such weapons are accurate and quick, firing with just the twitch of a finger, perfect for mowing down human beings, particularly if equipped with high-capacity magazines. They have become the weapon of choice of people intent on mayhem, most recently Omar Mateen in Orlando, who brought an AR-15 semiautomatic rifle to the packed nightclub where he killed 49 and wounded 53 early Sunday.

Conveniently for aspiring mass killers, such weapons are easy to buy legally in most states. Which is one reason that after just about every mass shooting, there are calls for a national ban on this style of weapon, originally designed for war. And to outlaw the high-capacity magazines, with more than 10 rounds, that help make them so deadly.

Would these bans prevent all mass shootings? Of course not. Are they a substitute for doing everything possible to identify and thwart would-be Islamic terrorists? No. Would the bans save lives and make it harder to carry out mass murder? Yes. And that alone makes them worth doing.

Gun laws don’t deter terrorists: Opposing view

Assault weapons were banned once before, for a decade starting in 1994. Law-abiding citizens were still able to defend themselves. Hunters were still able to hunt. Mass shootings did not end, but two studies suggest that the law helped by gradually reducing the number of assault weapons used in crimes.

While assault weapons equipped with high-capacity magazines are used in only a small percentage of crimes, holding down the size of magazines could save lives, Johns Hopkins' researchers reported in 2012. Even if the ban eventually prevented only 20% of those incidents, that would translate into 100 fewer homicides and 500 fewer people wounded by gunshots per year.

The 1994 law might have been even more successful had it been crafted more strictly. But gun makers are adept at finding legal loopholes, and this was no exception. They tweaked their products and sold the revised version legally.

A tighter measure could do more, while explicitly exempting hundreds of hunting rifles and shotguns. An attempt to do just that failed in the Senate in 2013, even in the wake of the massacre of elementary schoolchildren. The ever-powerful gun lobby stands in the way of such logical changes by twisting any move to limit the sale of certain kinds of guns into a menacing attempt to take away all guns.

The abundance of assault weapons, and the ease with which they can be purchased in the USA, is a gap that gives mass shooters an edge and has buoyed even the nation’s worst enemies. An American-born spokesman for al-Qaeda observed in a 2011 video that “America is awash with easily obtainable firearms” and asked aspiring killers, “So what are you waiting for?”

As Americans mourn the deaths of 49 innocent people, they should be asking the same question of members of Congress standing in the way of commonsense gun safety measures.

USA TODAY's editorial opinions are decided by its Editorial Board, separate from the news staff. Most editorials are coupled with an opposing view — a unique USA TODAY feature.

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