found: Walker, Robert E. A field guide to ghost guns, 2022galley (the term "ghost guns" will almost certainly become a familiar and often used phrase in the public discourse) publisher's description (Kits are available for hobbyists, as are 3-D printable gun designs, downloadable from the Internet in some cases. This concept has garnered the term "Ghost Guns": firearms whose existence is not reported to any third party and therefore whose existence is unknown and, largely, untraceable) (DLC)2021023015
found: Merriam-Webster, viewed July 1, 2021(ghost gun; a gun that lacks a serial number by which it can be identified and that is typically assembled by the user (as from purchased or homemade components); first known use in the meaning defined above, 2012)
found: Readers' guide, viewed July 1, 2021(in titles: ghost guns; assigned subjects: firearms, plastic guns)
found: Bing search, viewed July 1, 2021(over 200 million search results on search on home built firearms; with titles including terms Homemade guns; Kit guns; ghost guns)
notfound: InspecEngineering indexApplied science full text