Part 1 - Homemade Weapons: The Zip Gun

First I'd like to say sorry for No Post yesterday.
Google has been working on their Blogs and apparently this disabled the automatic upload file post feature I set and use each day.

This is Part One of Homemade Weapons.
I have not tried any of these myself and don't personally know anyone who has. Build this at your own risk.
Warning: Improvised and Homemade Weapons including Zip Guns are illegal in the United States unless you have a federal license.

Data is complied from various sources.

Improvised Firearms

An improvised firearm is a firearm manufactured by someone who is not a regular maker of firearms, such as a firearms manufacturer or a gunsmith, and are typically constructed by adapting existing materials to the purpose. Improvised firearms are often crude and illegally made.
Improvised firearms go by many names, such as zip gun in the United States, and sumpak, paliuntod, or paltik in the Philippines.
Zip guns are commonly found throughout the world.
The most popular countries for Zip Guns are:
The United States (mostly teenagers).
Philippines
China
India

Construction of a Zip Gun:
The essential part of any improvised firearm is the barrel and chamber. For small, low pressure cartridges, like the common .22 caliber (5.56 mm) rimfire cartridges, even very thin walled tubing will suffice. Zip Guns were used in the 1950's and 60's by gangs in New York City made from tubing used in coffee percolators or automobile radio antennas, strapped to a block of wood to serve as a handle. A rubber band provides the power for the firing pin, which is pulled back and released to fire. The use of such weak tubing results in a firearm that can be more dangerous to the shooter than the target; the poorly fitting smooth-bore barrel provides little accuracy, and is liable to burst upon firing, injuring the shooter.

Leveraging Other Items to make a Zip Gun:
More advanced improvised guns can leverage parts from other gun-like products. One example is the cap gun. A cap gun can be disassembled, and a barrel added, turning the toy gun into a real one; a firing pin can then be added to the hammer, to concentrate the force onto the primer of the cartridge. If the cap gun has a strong enough hammer spring, the existing trigger mechanism can be used as-is, otherwise rubber bands may be added to increase the power of the hammer.
Air guns have also been modified to convert them to firearms. The Brocock Air Cartridge System, or BACS, for example, uses a self contained "cartridge" roughly the size of a .38 Caliber Special cartridge, which contains an air reservoir, valve, and a .22 caliber (5.5mm) pellet. Examples of BACS airguns converted to firearms, either by drilling the barrel out to fire a .38 Special cartridge or by altering the cylinder to accept .22 caliber cartridges, have been used in a number of crimes. This has in resulted in legislation that classifies the BACS air guns as firearms, which effectively banned them in the United Kingdom in 2004.
Blank firing or starter guns can also be converted by adding a barrel

Background Use:
Improvised firearms are not solely the province of the criminal element, however; they are also used by insurgents. During the Japanese occupation of the Philippines during World War II, the paliuntod, a type of improvised shotgun, was commonly used by guerrillas and American soldiers who remained behind after Douglas Mac Aurthur's withdrawal. Made of two pieces of pipe that fit snugly together, the paliuntod was a simple, single shot open bolt design. The shell was placed in the breech of the barrel, which was then fitted into the larger diameter receiver. The receiver was capped at the breach end, and had a fixed firing pin placed to strike the primer of the shell. When the barrel was pulled sharply to the rear, the firing pin would strike the primer and fire the gun. These improvised firearms are still in use by both criminals and rebels in the Philippines

The Making of a Homemade Zip Gun:
Most Zip Guns are simple to make. The 22 caliber round is usually selected because it has no recoil, low pressure, and less chance to blow up in your face. They are made from plumbing pipe such as 1/8 inch for barrel.

Typical crude 22 Caliber Zip Gun (2 views, side and barrel).
This is what most thugs (hoodlums) build.
























U.S. Homemade 22 Caliber Zip Gun.
Look at the detail this person spent on making this.









Made in USA.
A crude but effective homemade shotgun.











Crude Indian Homemade Gun
(captured by police in India)
This weapon was interchangeable and capable of firing two different caliber bullets as shown in the photo.