Outdated worry
"the Undetectable Firearms Act of 1988, which bans the possession and manufacturing of firearms that can pass undetected through airport security"
It seems the new airport security scanners can detect an unused tissue in the pocket of my jeans, so should have no problem showing an all-plastic gun. The new scanners are not detecting metal, so the metallic content is not really relevant. It seems that law may have outlived its usefulness.