What I envision this technology doing is to make one-off and custom parts for others. Like a PVS14 adapter, that could have been made that way as could a mag. lever for a scope, etc., etc.
I'd like one. But I think I should focus on a mill and lathe after I move, and if I still have a place for one and can use it, I may get one then. Way, way off in the future I'd suspect.
There are metal printers and I'd be surprised if they couldn't print a firearm, not sure about the barrel but everything else, yeah. They use 'em to make custom medical implants including hips already. HOWEVER, BOTH (may be more now?) machines are owned by one guy IIRC, and you can't buy either one, you can only lease them. That way he has full control of what they do. He uses an algorithm to determine if you are making firearms parts (triangulation of pin holes, juxtaposition of geometries, etc.) and if you try it, they'll come take your machine and expect you to still pay them.
