A Study and Initial Design of Automatic Small Firearm

Abstract

The purpose of this study is to research and develop a gas piston automatic rifle to understand the design that can be further developed in the future. This is achieved by using theory alongside the motion simulation of the Emtan M4A1 rifle as a starting point for determining variables for design and studying the relationship between the motion distance of the piston rod, firing rate, spring constant, force in the piston rod, and the size of the gas port. The study found that the motion distance of the piston rod has a nonlinear effect on other variables over a wide stroke range, but it can be approximated linearly over a shorter stroke range. To ensure that the rifle meets the initial requirements with a firing rate of 950 rounds per minute, the suitable piston rod length should be between 1.3 to 1.5 inches according to the desired design specifications. The results from this analysis have been used for preliminary design and motion simulation, showing that the obtained values are consistent with theory, although there are still discrepancies that need to be addressed and further developed.