A Bay State man was sentenced to just shy of six years in federal prison Tuesday for illegally possessing AR-15 assault-style rifles, which he assembled in his home state and sold in New Hampshire.

Raymond L. Blackmer III, a resident of Easthampton, Mass., did not contest the 70-month sentence, which was handed down as part of a plea deal he reached with prosecutors in late July.

Blackmer previously pleaded guilty in U.S. District Court in Concord to one count of illegal possession of a firearm by a convicted felon.

The 70-month prison term exceeds the federal sentencing guideline range. But even under those conditions, Blackmer agreed to plead guilty in New Hampshire to avoid further prosecution on similar charges in Massachusetts, his attorney, Jonathan Saxe, told the court.

“From the beginning, he said, ‘I know what I did was wrong,’ ” Saxe said of Blackmer’s decision to accept responsibility and admit to the crime.

The Easthampton (Mass.) Police Department began its investigation in 2015 of Blackmer, who they say was dealing narcotics. But that investigation took a turn when police learned Blackmer was also purchasing component parts for firearms on the Internet and selling those assembled rifles over state lines.

Police say Blackmer sold finished firearms in the Granite State, where he profited about $300 per rifle.

In November 2015, police pulled Blackmer over in Winchester and executed a federal search warrant of his vehicle. Police seized two AR-15-style rifles, two sets of rifle sights, and a fully-loaded, 30-round AR-15-style magazine. 

Additional search warrants were executed at his residence and workshop.

Blackmer has a lengthy criminal history that includes convictions in the late 1980s for child rape, as well as assault and battery with a dangerous weapon, according to court records. 

Saxe said Tuesday that Blackmer has a long history of substance abuse, which began at age nine when he first tried marijuana. He said Blackmer later got hooked on cocaine before switching to heroin and other opioids.

Blackmer briefly addressed the court at his sentencing hearing about his hopes for recovery: “I know I screwed up. . . I can’t continue on this pattern. It’s taken too much of my life.”

(Alyssa Dandrea can be reached at 369-3319, adandrea@cmonitor.com or on Twitter @_ADandrea.)