There was a short mention in Peter Telep's Descent: Stealing Thunder, of a gun that made our/your standard of "concealed carry" seem a little tame.
It was an automatic rifle called a "flight-piece". Judging by the small part it has in the novel, it sounds about the size of an M4. The reason for the expense was that it could project a cloaking field around itself, rendering it invisible to all visual and electronic scanning devices, which would probably include X-Ray scanners.
The gun gets a short description in a single paragraph, when the father of the boy that was murdered for a secret control chip walks up to the offices of the murderer's employers, and opens fire, killing security, civilians, and even a child.