Abstract

This study analyzes the influence of lubrication treatments on the force absorbed by the breech bolt called push-out force. The results are of high interest for weapon-safety and durability studies, especially when it comes to weapon maintenance. A barrel-ammunition combination represents an expanding vessel under high pressure. The pressure rises from ambient up to 420 MPa in less than a millisecond. During such a highly dynamic process, purely static equations, describing the problem of the casing push-out force, may not be applied. Besides the dynamic behavior, the surface properties and geometry also play an important role. To investigate the push-out force, a measurement system based on a force washer was built. This system was validated using a crusher method and finite element analysis. The impulse was calculated using the data of the measured force to obtain additional information about the force-time properties of the push-out behavior. Untreated ammunition and two lubrication systems: “ice layer” and “oil lubricated,” as well as seven different ammunition sizes ranging from 5.56 to 12.7 mm were considered. The response was the force absorbed by the bolt while the cartridge provides rear obturation to the combustion gases. It was found that both the casing geometry and its treatments have a significant influence on the push-out force.

Highlights

  • The aim of this contribution is to measure the influence of differently treated cartridge surfaces on the breech-bolt force in a range of small-arms ammunition

  • The 9 mm Luger is the only casing without a bottleneck and has a unique push-out curve as compared to the other curves

  • This contribution investigated the effect of casings and surface states on the push-out force and transmitted impulse

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Summary

INTRODUCTION

The aim of this contribution is to measure the influence of differently treated cartridge surfaces on the breech-bolt force in a range of small-arms ammunition. Due to safety and functionality reasons, the chamber of the weapon needs to be sealed by the casing during the process of firing This sealing process decreases the breech-bolt force. Due to the internal pressure and the obturation process, the casing is pushed against the wall of the chamber In other words, it means that the overall push-out force is not entirely taken by the breech bolt. (1) The surface area of the case head where the pressure acts, (2) The pressure in the casing, (3) The friction between the chamber wall and the case body, (4) The material properties of the chamber and casing, (5) The chamber geometry, i.e., fluted or smooth By controlling these five factors and measuring the push-out force, it is possible to get information about the effect of the lubricant on the obturation process during firing. This study is a supplement to and enrichment of existing studies on diagnosis associated with the firing process for small-arms ammunition

EXPERIMENTAL PROCEDURES
RESULTS AND DISCUSSION
CONCLUSION
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