Printing a complete, functioning firearm is a far cry from an AR-15 lower. Do you realize what kind of pressure levels that the chamber and barrel must withstand?
A decent machine shop can make all kinds of firearms today though. As far as suppression goes, that depends heavily on the ammunition.
Teflon coated bullets are pure media hype. The rounds were armor piercing because of the tungsten alloy they were made from. The teflon coating was used to help reduce barrel wear. Most high powered rifle rounds, which can be purchased just about anywhere today, are armor piercing.
3d printers will never make something capable of withstanding firing pressures. Now, home CNC machines.... that's a little more likely. The thing is, a "machine shop" is getting to the point where it's hobby-level stuff. Where two decades ago, a hobbyist might have had a router, maybe a lathe, two decades from now they're going to have a CNC, and 3d printer, and who knows what else. Hobbyists will be able to churn out anything from a drone aircraft to a fully functional firearm, in just a few days in the workshop. Media attention has so far focused on the impact of that fact on the manufacturing industry, but neglected its impact on government.