Threat of plastic guns grows as undetectable firearm law set to expire.

Federal law enforcement authorities are raising concerns new, futuristic 3-D printed guns made entirely out of plastic could pose a myriad of security threats across the U.S., as a law banning undetectable firearms is set to expire.

3-D industrial printers that can create plastic models and prototypes can make workable guns that can't be picked up by metal detectors, and officials say they could pose a threat to countless government institutions, schools and other buildings.

A longtime ban on undetectable firearms is scheduled to expire Dec. 9 and two Democratic senators, Chuck Schumer of New York and Bill Nelson of Florida, have called for a ban on plastic guns. Rep. Steve Israel, D-N.Y., also has introduced legislation on the issue.

"The expiration of this law, combined with advances in 3-D printing, make what was once a hypothetical threat into a terrifying reality," said Schumer. "We are actively exploring all options to pass legislation that will eliminate the problem."

In a meeting with reporters Wednesday, agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives said plastic guns present a special challenge for law enforcement agencies.

The agents said that in order to comply with current law, a person manufacturing a gun must use a certain amount of metal in the finished product so that the firearm is detectable by scanners at airports, federal buildings, sporting events -- any place where security screening is in place. If the law expires, someone could legally make and sell firearms that are undetectable.

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