Raytheon is exploring 3D-printed missiles:
"“You can design internal features that might be impossible to machine,” said Raytheon engineer Travis Mayberry, who is researching future uses of additive manufacturing and 3-D printing. “We’re trying new designs for thermal improvements and lightweight structures, things we couldn’t achieve with any other manufacturing method.”
With commercially available high-end equipment and specially modified versions of low-cost 3-D printers, Raytheon researchers have created nearly every component of a guided weapon using 3-D printing, including rocket engines, fins, parts for the guidance and control systems, and more."
http://uproxx.com/technology/2015/07/3d-printed-missiles-raytheon/