quoted from an ATF ruling...
"ATF and its predecessor agency, the Internal Revenue Service (IRS), have historically held that the original, crank-operated Gatling Gun, and replicas thereof, are not automatic firearms or machineguns as defined. See Rev. Rul. 55-528, 1955-2 C.B. 482. The original Gatling Gun is a rapid-firing, hand-operated weapon. The rate of fire is regulated by the rapidity of the hand cranking movement, manually controlled by the operator. It is not a "machinegun" as that term is defined in 26 U.S.C. 5845(b) because it is not a weapon that fires automatically"
http://www.atf.gov/regulations-rulin...ng-2004-5.html