Someone made an AR lower that worked for 6 shots. If they had used stainless and sintered it, it may have shot more. So it can be done.
In a few years, who knows, maybe a barrel if you print metal with a polymer binder then heat treat.
Maybe, binders and sintered are cool don’t get me wrong, but for now it is gears for your window mechanism in your car door, not some high stress item. “Single Crystal” technology is sort of related, but I don’t see this being done by a laser it complicated.