They are not undetectable you idiots.
There are plenty of metal parts in the damn thing from the barrel to the receiver and the spring at a minimum ...
The barrel is all plastic from what I could see in the youtube video. I think the only metal part was the firing pin which was made from a common nail.
There are plenty of metal parts in the damn thing from the barrel to the receiver and the spring at a minimum ...
Normal productions guns would be. These are completely plastic except for a nail used for the firing pin. You're not gonna get more than one or two shots out of one of these things, max. The idea is similar to the 'liberator' we dropped into Europe during WWII. You use the disposable gun to get a real one from the occupying forces.
The description of the uprising in the Warsaw ghetto in the book "Unintended Consequences" is a really good description of this.
This is really just a stunt to prove it can be done. Like someone upthread said, it's not really even new. Anyone competent with machine tools can make something similar out of sheet metal and a piece of pipe. Personally I'd feel better using something homemade out of metal, but if it's all you have to get the tools, of liberty, plastic will do.
Pretty good bet that a small piece of some type of common ceramic/composite rod could replace even that.