FACTORS AFFECTING BOLT THRUST AND EXTRACTION FORCES IN SMALL CALIBER WEAPON SYSTEMS

Abstract

The brass cartridge case has been the standard for small caliber weapons systems since the late 1800’s. While brass has ideal material properties allowing for obturation during pressurization with enough elastic recovery for extraction, its high density makes its overall weight undesirable. In addition, next generation weapon systems are firing at pressures far higher than legacy systems, necessitating higher strength materials due to structural concerns. Previous work completed looked at the bolt thrust and extraction forces variations when the case material was varied between brass, high strength steel, and polymers. It was found that bolt thrust varied as much as 66% based off cartridge case material. It also showed that the use of Finite Element Analysis has good agreement with experimental results and could be used as a predictive tool. This report will examine additional factors within the weapon system affecting bolt thrust and extraction forces. Differences of friction coefficients and friction conditions within the chamber will be explored. In addition, weapon headspacing variations are considered. These will be coupled with the variations in materials previously studied to determine each material’s sensitivity to weapon conditions.