If it was for training purposes it wouldn’t be mounted all the time. In the Abrams we had an in-bore subcaliber device. It was mounted right in the gun tube and the bullet was fired through the tube for training. Those M2s mounted over the main gun are for combat. Either firing spotting rounds or for engaging targets that don’t require the main gun.
That’s what I was going to say- they look like something out of a game.