That punk pulled a Glock 7 on me! You know what that is? It's a porcelain gun made in Germany. It doesn't show up on your airport X-ray machines, and it cost more than you make here in a month. 

- Bruce Willis, in Die Hard 2 (1990)

Now, Hollywood isn't renowned for it's portrayal of reality, but I cannot believe how many people still believe there is such a thing as a 'plastic pistol, undetectable by x-ray machines'.

Most of the time when people talk about "plastic" guns, they are referring to Glocks. Glocks have polymer frames which makes them lighter and more comfortable to carry for longer periods. The barrel and internal components of the gun, however, are made from metal which show up nicely under any x-ray machine.

The slide makes up the bulk of the weight of an unloaded Glock. Trust me on this one, when you hold it, there's no mistaking it for 'plastic'.