What was the first swing-out cylinder, DA revolver adopted by the U.S. military?

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What was the first swing-out cylinder, DA revolver adopted by the U.S. military?
Colt M1889
Colt M1917
Smith & Wesson M686
Smith & Wesson Triple-lock
Webley MK IV

How many barrels does a traditional Gatling gun have?
4
6
7
8
10

Who invented fire sprinklers, curling irons and steam-powered aircraft as well as the famous gun that carries his name?
Samuel Colt
John Garand
Paul Mauser
Sir Hiram Maxim
John Thompson