If you can print a gun, you can print many other kinds of machinery. The day may not be very far off when you can start with half a ton of aluminum and stainless steel powder, and print yourself a Ferrari with a V-12 engine.
Totally practical, you could do most of it now, (large parts are difficult) The trouble is it would cost a lot more than just going to a dealer and buying one.
I've been using various plastic part additive manufacturing methods (mainly SLS / SLA) for a few years now. It works great when you want one of something or ten of something: A gun sized object may cost you a couple of hundred dollars a part, so Its much cheaper than spending $10-20,000 on the tooling, but when you have that tooling the cost falls to pennies.
People (including some of my customers!) tend to look at a mass produced item and think that a comparable specialised piece of equipment should cost about the same. Its not so. Even a Ferrari is 'mass produced' from the manufacturing method point of view.