The U.S. House of Representatives passed a bill on Tuesday to extend for 10 years a ban against firearms that cannot be detected with metal detectors or X-ray scanners.
On a voice vote, the Republican-led House sent the measure to the Democratic-led Senate, which is expected to consider a tougher alternative before likely approving it.
U.S. Attorney General Eric Holder urged Congress last month to extend the ban, citing a proliferation of plastic guns made with 3-D printers.
While the House has agreed on little this year, contributing to one of the most unproductive and unpopular Congresses ever, it passed the bill with bipartisan support despite reservations by a number of Democrats that it does not go far enough.
Democratic Senator Charles Schumer of New York has proposed plugging "a loophole" in the ban by requiring that all firearms include at least four ounces of metal that cannot be removed.
Without such a provision, Schumer and others warn, the metal could be taken off the firearm, allowing it to avoid detection and be carried into a supposedly secure area.
Schumer does not have much time to make his case. The ban expires on Monday, the day the Senate returns from a two-week recess.
On that day, Democrats may try to quickly approve Schumer's proposal with the unanimous consent of the Senate.
If that fails, as anticipated, the Senate is expected to give final approval to the House passed bill, clearing the way for President Barack Obama to sign it into law.
Democratic Representative Steve Israel of New York joined Republican Representative Howard Coble of North Carolina in drafting the House bill. Like Schumer, Israel prefers a stricter measure, but said at a minimum wants an extension of the ban.
"We now have enough momentum to pass an extension of the ban before December 9. But we don't have enough momentum to pass a modernization of the ban before December 9," Israel said.
"But once we pass this bill, we need to make sure bad guys can't skirt the law," said Israel, voicing confidence that the law will be strengthened. "It's common sense."
Representative Hal Rogers of Kentucky, a leading Republican, expressed concerns of his own, and said, "I'll be looking to tighten up the process."
Israel has proposed requiring that two major components for a handgun and three major components for a rifle be made of unremovable metal.
Earlier this year, the U.S. gun lobby helped defeat tougher gun control sought by Obama in wake of a massacre at an elementary school in Newtown, Conn.
Overall, the gun industry has not said much about the drive to extend the ban on undetectable guns, but backers believe fear of the industry is a reason why the House bill was not tougher.
Winnie Stachelberg, an executive director of the Center for American Politics, a liberal advocacy group, denounced the House bill as inadequate.
"We urge Congress to put public safety ahead of craven politics by enacting comprehensive legislation," Stachelberg said.
Israel said the National Rifle Association, one of the most influential lobbying groups in Washington, had been essentially silent on the effort to renew the ban.
But the National Shooting Sports Foundation, a trade association for the firearms and ammunition industry, backed the extension in a letter to Congress.
"The current law has proven effective," wrote Lawrence Keane, the foundation's senior vice president and general counsel.
Keane said on Tuesday, however, that his group opposes proposals to toughen the ban, dismissing them as excessive and potentially harmful to the legal manufacturing of firearms.
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