[GreenLanternCorps]

The problem with the Gatling Gun in the civil war was that they tended to treat it as artillery, not like a machine gun.

It was not a long range weapon. Had they embedded them with infantry or dismounted cavalry, they could have been devastating. Imagine first day Gettysburg if Buford had Gatlings...

[BroJoeK]

Agreed.
Somewhere, seems like I read that a major Union concern, and not just in the Civil War, is that soldiers might use up too much ammunition.
I get the impression they were confused about the necessary connections between shooting at the enemy and winning battles.