Defendant failed to register the devices or comply with regulations. The United States Attorney’s Office for the District of Colorado announced that Bradley Bunn, 55, of Loveland, Colorado, pleaded guilty to one count of making destructive devices and four counts of possessing destructive devices in violation of Title 26, United States Code, Section 5861.  Each count carries a maximum potential penalty of 10 years imprisonment, followed by three years of supervised release.  Bunn was remanded to the custody of the U.S. Marshals following today’s hearing before U.S. District Judge Christine Arguello.  A sentencing hearing is scheduled for June 3, 2021. According to the facts contained in the plea agreement, on May 1, 2020, the FBI executed two search warrants at Bunn’s home.  They found four explosive devices.  Each device consisted of galvanized steel pipe with end caps and a fuse.  The devices measured 2 inches in diameter and between 13.5 and 9.25 inches in length.  FBI Bomb Technicians concluded that each of the devices was filled with explosive materials.  Agents recovered additional bomb-making components in the house, including more steel pipes, end caps, primers, fuses, and bottles of smokeless powder.  The defendant had not registered the devices in the National Firearms Registration and Transfer Record and he had not complied with any regulations concerning the making of destructive devices. 

via justice.gov: Northern Colorado Man Pleads Guilty For Possessing Pipe Bombs