From what I remember of Gatling guns, the US Quartermaster declined to buy them during the Civil War. The gun itself was about 800lbs, with a support wagon that was another 800lbs.
The round was .58 cal, so it wasn’t already provisioned by the quartermaster corps.
And, the gun itself wasn’t reliable.
What it was a decade+ later, I have no idea.
Take a look at RedMonqey’s post #81. He shot my Gatling Gun theory full of holes (pun intended).