Just to add to the confusion - in 1981, at the request of the AMU, the small arms shop at Anniston Army depot milled off the receiver extension to which the auto selector is fitted on three m14's. They were then reassembled and test fired to see if the process affected accuracy or functioning. I understand the reasoning was to see if the rifles could be modified so as to never be converted to full auto and then sold to civilian competitors. Another rumor was that the army wanted m21 rifles without the selector - who knows!The rifles worked fine, the report was forwarded and nothing ever happened, The three rifles were supposedly sentenced to meet cptn crunch