Schematics for a 12mm pistol

This delightfully colorful pamphlet shows you how to craft your own Hammerhead ballistic dispatch mechanism, or "gun" as they are sometimes called. All the instructions required are right here at your fingertips. An exceedingly clever logo depicts a brawny humanoid with a head shaped like... you guessed it... a hammer.
It tells you how to make a Hammerhead 12mm automatic pistol with the following components:
 1 - brick of quick-mold plastic 
 1 - firearm trigger assembly 
 1 - firearm breech assembly 
 1 - ammunition magazine assembly 
 1 - short steel pipe 
 1 - firearm sight assembly 
Making this would take expertise in craft and good familiarity with pistols.
In the upper right corner is a note: 'First discovered by Dr. Dr.Crowley.'
==Components==
*Brick of quick-mold plastic
*Firearm trigger assembly
*Firearm breech assembly
*Ammunition magazine assembly
*Short steel pipe
*Firearm sight assembly