A Roanoke County man was convicted Monday of having a machine gun among the collection of high-power firearms he kept in the basement of his Verndale Drive home.

Samuel Morris Overstreet, 47, will face up to 20 years in prison when he is sentenced later in U.S. District Court in Roanoke.

It is illegal to possess a machine gun without a permit from the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives. Not only did Overstreet not have a permit, he was also prohibited from owning any guns after being committed to a psychiatric hospital.

An ATF spokeswoman in Washington would not say how many machine gun permits the agency has issued in Virginia. Such information is proprietary, the spokeswoman said.

After a jury was seated Monday to hear Overstreet's case, he decided at the last minute to plead guilty to possessing an unregistered machine gun and having guns after being committed to a mental institution.

In December 2003, Overstreet called police to complain about trash cans being knocked over in his Northeast County neighborhood. A short time later, an officer stopped by to talk.

After the conversation turned to Overstreet's guns, authorities obtained a search warrant and discovered what Assistant U.S. Attorney Andrew Bassford called a "fairly extensive" arsenal in the basement. About 7,000 rounds of ammunition were also found.

In addition to about 20 rifles, shotguns and handguns, federal agents seized the illegal machine gun and two unregistered silencers.

Overstreet told authorities that the silencers allowed him to fire his guns in his back yard without the neighbors hearing anything, Bassford said.

Defense Attorney Melvin Hill described his client as an avid gun collector who spent nearly $20,000 on his hobby. Hill said he did not think his client posed a threat.

What Overstreet actually had in his home was a kit to convert a MAK-90, a semi-automatic rifle similar to an AK-47, into a fully automatic weapon. But the law made no distinction between the kit and a converted gun.

Although the charges Overstreet pleaded guilty to carry up to 20 years in prison, both Hill and Bassford said sentencing guidelines in the case will likely call for a lesser punishment.

In 1990, Overstreet was committed to a mental hospital following a police standoff at his home. The incident began when Overstreet called WROV-FM and asked the radio station to play "Eye of the Hurricane." He told disc jockeys the song reminded him of the death of his girlfriend, and that he was thinking about killing himself.

After barricading himself in his home for several hours, Overstreet was subdued by police.