ZipGun & 50-Caliber Rifle Construction Manual

The Zip, or Pen Gun, as it is sometimes referred to, is perhaps
the simplest of all improvised firearms and is usually found in
.22 calibre due to the relatively low pressures generated by
this small cartridge.
I decided that a need existed for a simple homemade version
of this tried and tested ‘’contraption’’ and came up with the
following design !
I designed this weapon with the caveat that it should be
buildable in one day or less, and I think I have achieved that
requirement.