there was a small 1893 'police' model gatling in .45-70
rate of fire was 'only' 800 rounds per minute.
if i recall, the crank operated gatling is legal without a machine gun licence from atf as it a manually loaded, cocked, and fired weapon. i recall seeing one in .22lr which is about the only way to afford the ammo, and even that ain't cheap or easy to find in bulk nowadays.
p.s. - the modern equivalent:
LINKY TO VIDEO