British subject Phillip A. Luty thumbed his nose at gun bans in the UK and designed a burp gun from homemade parts, then wrote a book about it.
We are talking bent sheet metal, wire springs, washers and hex screws without a single repurposed firearms part. The barrel on the crude blowback sub gun was handmade, as was the receiver and magazine. Made long before the days of 3D printed designs and without any machinery, the Luty pattern SMG was smoothbore and probably sucked to fire, but it did fire!
In conjunction with Armament Research Services, Ian with Forgotten Weapons visited the Royal Armouries’ National Firearms Centre and checked out a number of Luty’s actual working designs, which are covered in more detail here.