They’re just too damn easy to make.
Like, for instance, this home-made, full-auto shotgun.
EMBED-Home-Made Belt-Fed Shotgun – Watch more free videos
Yeah, it has feed problems. Yeah, I bet it’s not as rugged or as portable as a mil-spec unit of equivalent power and speed.
But it’s a home-made machine gun.
You can carve a full-auto AK-47 out of scrap metal with hand-tools. There’s villages in Afghanistan that make their living doing that.
There’s a guy in England who published, both on paper and on the net, instructions on building firearms, including cartridges and full-auto firearms, out of house hold supplies and plumbing parts. He’s in jail now — jailed, for exercising his free press rights — but the documents are out there. The information is free. I’ve got a paid for copy of one of his manuals (although not where I can get to it right now).
Look up the story of David Marshall Williams. He invented a new rifle mechanism while in prison, back in Prohibition days. It proved to be so revolutionary that he was freed and put to work developing the famous M-1.
I’ve read instructions for making a single-shot, desperation shotgun out of a rolled-up magazine or newspaper, some tape, and a thumbtack.
Zip guns like that, and smuggled in commercial firearms, are confiscated in prisons all the time.
You cannot keep guns out of the hands of people willing to break the law to get them.
All you can do is see to it that the law abiding are armed as well.