You seriously think you couldn't sneak a small caliber bullet in a hollow belt buckle, thick rimmed glasses, watch, in a laptop or phone, for some easy examples? No one said the 3D printed gun needed to be loaded BEFORE boarding the plane. Sneaking a bullet onto a plane used to be easier than sneaking the lead delivery device, until 3D printing came along. Now BOTH are easy to get on board undetected. This new gadget does absolutely nothing to mitigate the risk.
It doesn't look for gun-shaped objects. They would detect the brass casings in the magazine, however.3d printed guns are not capable of properly handling the chamber pressures of cartridges. Go on youtube and you can even find shotguns, much thinner barrels than a rifle or pistol, that are blow-out due to simple obstructions. It would only work if you had lower power bullets, probably custom loads since the chamber pressures would still be ridiculous for a plastic barrel.
it doesnt matter if the gun is plastic. The ammunition cant be made from plastic. even if plastic is strong enough for the case it isnt heavy enough for an effective bullet. wouldnt the potential cancer machines known as 3d body scanners detect this anyway?