As a unit Armor in the US Army, I would routinely have to check the barrels of our M9’s, M4’s, M14’s, M16’s, M240’s and M2’s with a specialized scope a light kit.
Cracks and abrasions can show up on the barrel, that the naked eye just cannot pick out while looking down the barrel like the woman in the picture.
And our dependence on technology, by using this scope and light kit has probably saved quite a few peoples fingers, hand or who knows what else from faulty barrels.
The US Army is a LARGE branch, and we don’t always have the resources to just replace barrels after the recommend amount of rounds have been fired out of them. So we make do, and just PMCS that shit.