This book was written to interest the reader in gun design. The gun industry needs and is due for the next big breakthrough. Every 100 years seems to bring the next big development in firearms technology. In the 1600's the wheel lock was developed and heralded the first use of firearms. In the 1700's came the flintlock musket. In the 1800's came the percussion cap and later in the century the thin brass shell to carry the powder, ball ammunition, and primer was perfected. While the 20th century has seen the invention of liquid propellant, caseless ammunition, and the gyrojet, the thin brass shell has been hard to beat and is still the dominant way to feed ammunition to the firearms of today. We are due for the next big advance, but from where will it come? This book was written to interest the reader on the simplicity and the hidden complexity that good gun designs exhibit and prompt the imagination of the reader to investigate the field of firearms design further. Reading this book will give the reader:* Two ways to calculate the round per minute level of a 9mm caliber submachine gun using the STEN submachine gun as an example and gives sample excel spreadsheets to allow the reader to experiment with different design conditions.* The full technical data package of a reverse engineered STEN Submachine gun. The drawings are shown as individual operation process sheets showing the dimensions for each separate cut on an individual drawing.* The cycle of operations of the STEN with illustrations.* The analysis and sample calculations to design a gun barrel.* A discussion of firearm metallurgy with recommendations on material selection and heat treatment for various components. This book is unique as it is not a picture book of firearms, a combat guide on how to use them, nor discusses their maintenance or care. It does expose the engineering that can go behind a gun design project. This book not only gives the reader the drawings for a gun but also explains the engineering and dynamics behind it.