A fed informant was sent to Weaver, requesting to cut a barrel of a shotgun, creating a short barrel shotgun. The feds then charged him with the NFA violation. Randy never made the SBR.
The judge had dropped the charge of the short barrel shotgun that Weaver never made. He failed to appear for court. That was the charge the feds came at him for.
They came, just a couple, with a suppressed rifle, evidence of intended assassination not arrest.
Some of Rectal Faced Reno, the Butcher of Waco's work. The federal agents who survived were charged by the state but never brought to justice. Randy did time for the Failure to Appear and won a small, paltry sum of money for the feds killing his son and wife.
This from my memory of the case.
Randy was stupid agreeing to saw the end off a shotgun supplied by the informant. The feds under Clinton and Janet Reno wanted examples of White Supremacy being put down violently and publicly. Both Waco and Ruby Ridge backfired spectacularly.