in 1931, the colt arms co. made the colt monitor automatic machine rifle (r 80). this was mostly meant to be used by prison guards and the police. the colt monitor did not have a bipod. the colt monitor weighed around 16 lb. 3 oz. without any ammunition in it. it had a rate of fire of around 500 rpm. around 125 colt monitor automatic rifles were made. 90 of these were bought by the fbi. eleven rifles went to the u.s. treasury department in 1934. the rest went to many prisons, banks, security companies and police departments.