A Willmar, Minn., man pleaded guilty Thursday to possessing unregistered machine guns, silencers and pipe bombs retrieved by authorities who found an arsenal on his property earlier this year.

Chad Lee Monson, 46, told a Minneapolis federal judge that he knew he was barred from handling the weapons because of a previous drug charge. Some of the weapons found at his home and at a nearby pole barn were once registered in a federal licensing database, but Monson admitted to letting their registration lapse and also to owning an Uzi machine gun illegally modified to fire fully automatic.

Monson’s plea agreement whittled his 18-count federal indictment down to three charges. On Thursday, U.S. District Judge Joan Ericksen said that, taken together, the charges carry a maximum 30-year possible sentence. The judge did not immediately set a date for Monson’s sentencing, which she said will include a provision prohibiting him from possessing any weapons and ammunition. He will also be ordered to legally divest himself of any weapons not already taken by law enforcement officers.

His brief plea hearing made no mention of prior allegations that Monson vowed to target attorneys and a judge with bombs, which factored heavily into a federal magistrate judge’s decision to keep Monson detained before sentencing. Previous state charges cited an unnamed informant as disclosing the threats, and, at a June hearing in the federal case, Assistant U.S. Attorney John Docherty said Monson also made threats when authorities seized weapons and methamphetamine from his property this year.

But in a brief interview after Thursday’s hearing, Daniel Mohs, Monson’s attorney, said his client was a gun collector who used the pipe bombs as part of his excavation business. Any talk of Monson harboring visions of targeted bombings, Mohs said, was “blown out of proportion.”

“If there’s a lesson to be learned from this, it’s if you’re going to be collecting things like guns and silencers, know what you are collecting and that no one else has access,” Mohs said.

“He just had them all over the freaking place.”