Three Percenterism is not a group, but a sub-ideology or common belief that falls within the larger antigovernment militia movement. Three Percenters (also known as III%ers or Threepers) claim that only 3% of American colonists fought against the British during the American Revolution, a claim that has never been proven.
https://www.splcenter.org/fighting-hate/extremist-files/group/three-percenters