A 50-year-old Glassboro man, who turned his home into an arsenal with hundreds of guns, has pleaded guilty to selling an assault firearm to an undercover state trooper and possessing other illegal weapons, authorities said Tuesday.

Horace Dixon was arrested by state troopers Aug. 13, 2009, in the parking lot of a bowling alley on Route 47 in Glassboro where he came to sell guns - unknowingly to a state police detective.

Dixon faces 10 years in state prison, including five years without possibility of parole, under a state-recommended plea agreement. Gloucester County Superior Court Judge Walter L. Marshall Jr. scheduled sentencing for Jan. 28.

Dixon pleaded guilty Monday to unlawful disposition of an assault firearm, unlawful possession of a machine gun, and unlawful possession of a handgun.

The charges against him were part of a May 20, 2010, state grand jury indictment stemming from an investigation by the New Jersey State Police/Alcohol, Tobacco and Firearms (ATF) Joint Firearms Task Force, Glassboro Police Department, and Gloucester County Prosecutor's Office.

"By putting gun traffickers such as this defendant behind bars, we are eliminating a conduit by which deadly assault weapons are reaching the streets of New Jersey," state Attorney General Paula Dow said Tuesday.

The partnership of state police and the ATF will "continue to aggressively investigate and prosecute gun traffickers who sell illegal weapons to anyone willing to pay their price," added Criminal Justice Director Stephen J. Taylor.

The Dixon investigation began at the local level but grew to include county, state and federal agencies, according to Col. Rick Fuentes, superintendent of the New Jersey State Police.

"This case involved a man whose home was an arsenal of dangerous guns and whose actions displayed a complete lack of concern for how the illegal firearms he sold were to be used," Fuentes said.

The Glassboro Police Department originally learned about two assault rifles for sale and contacted the ATF in early July 2009.

Using the information, a state police detective, acting undercover as part of the Joint Firearms Task Force, contacted Dixon to purchase four weapons and told him he would deface the guns' serial numbers to sell them on the street.

Dixon sold the undercover detective two semiautomatic rifles, along with ammunition, on July 17, 2009, authorities said. He sold two more guns - a pistol and semiautomatic rifle - and ammunition magazines to the undercover detective for $2,000 on Aug. 7, 2009.

After Dixon's arrest, police executed a search warrant for his car and seized two semiautomatic pistols, a 12-gauge pump-action shotgun, a semiautomatic rifle, and a large-capacity magazine for the rifle.

At Dixon's home, they also found a grenade launcher and more than 200 guns, including a belt-fed machine gun and semiautomatic rifles.

Dixon specifically pleaded guilty to selling the semiautomatic rifle to the detective and to possessing a pistol and machine gun.

Contact staff writer Edward Colimore at 856-779-3833 or ecolimore@phillynews.com.