Influence of chamber misalignment on cased telescoped(CT) ammunition accuracy

As part of a research program, it was desired to better understand the impact of the rotating chamber alignment with the barrel throat on the precision and accuracy of a novel cased telescoped(CT) ammunition firing rifle. In order to perform the study, a baseline CT ammunition chamber which was concentric with a Mann barrel bore was manufactured. Additionally, six chambers were manufactured with an offset relative to the barrel bore. These chambers were used to simulate a misaligned chamber relative to the bore axis. Precision and accuracy tests were then performed at 200 m in an indoor range under controlled conditions. For this project, 5.56 mm CT ammunition was used. As the chamber axis offset relative to the gun bore was increased, the mean point of impact was displaced away from the target center. The shift in the impact location is explained by the presence of in-bore yaw which results in lateral throw-off and aerodynamic jump components. The linear theory of ballistics is used to establish a relationship between the chamber misalignment and the resulting projectile mean point of impact for a rifle developed to fire CT ammunition. This relationship allows for the prediction of the mean point of impact given a chamber misalignment.

A statistical method for the evaluation of projectile dispersion

As part of a research program, an extensive study on the dispersion characteristics of eight different7.62 ? 51 mm ammunition types was conducted. The paper presents the main steps in the experimental and analytical process carried out to evaluate, namely to measure and compare, the dispersion characteristics of the ammunitions; namely,(1) identify the number of rounds to fire in the trials,(2) establish a test plan and the setup for the precision trials,(3) fire the rounds, following an established protocol for the experiments,(4) collect the impact points, and measure the performance through statistical measures,(5) perform a statistical analysis of dispersion applied to the results obtained in the trials, and(6)conclude on the ammunition characteristics. In particular, the paper proposes a statistical method to evaluate the precision of ammunitions fired with precision(Mann) barrels. The practical method relies on comparison of confidence intervals and hypothesis testing on the standard deviation of samples,namely the impact points. An algorithm is proposed to compare the variances of two or more populations of ammunitions.

Validation of the NATO Armaments Ballistic Kernel for use in small-arms fire control systems

In support for the development of a new small-arm ballistic computer based on the NATO Armaments Ballistic Kernel(NABK) for the Canadian snipers, DRDC Valcartier Research Centre was asked to carry out high-fidelity 6 degree-of-freedom(6-DOF) trajectory simulations for a set of relevant vignettes for the snipers, and to compare the direct fire 6-DOF simulation results with those obtained with the 4-DOF NATO Armaments Ballistic Kernel(NABK) adapted to simulate small-arm ammunition trajectories. To conduct this study, DRDC Valcartier Research Centre used BALCO v1.0b. This paper presents(1) the process and the methodology employed to carry out the sniper direct fire solution study,(2) the modeling and the simulation of the sniper projectile, the approach used in calculating the firing solutions, and the results of direct fire simulations for the sniper vignettes, and(3) an analysis of firing solutions obtained with the BALCO engine versus those of NABK. The work presented in this paper serves to validate the use of NABK for the new sniper ballistic computer.

A comparison of piecewise cubic Hermite interpolating polynomials,cubic splines and piecewise linear functions for the approximation of projectile aerodynamics

Modelling and simulation of projectile flight is at the core of ballistic computer software and is essential to the study of performance of rifles and projectiles in various engagement conditions.An effective and representative numerical model of projectile flight requires a relatively good approximation of the aerodynamics.The aerodynamic coefficients of the projectile model should be described as a series of piecewise polynomial functions of the Mach number that ideally meet the following conditions:they are continuous,differentiable at least once,and have a relatively low degree.The paper provides the steps needed to generate such piecewise polynomial functions using readily available tools,and then compares Piecewise Cubic Hermite Interpolating Polynomial(PCHIP),cubic splines,and piecewise linear functions,and their variant,as potential curve fitting methods to approximate the aerodynamics of a generic small arms projectile.A key contribution of the paper is the application of PCHIP to the approximation of projectile aerodynamics,and its evaluation against a set of criteria.Finally,the paper provides a baseline assessment of the impact of the polynomial functions on flight trajectory predictions obtained with 6-degree-of-freedom simulations of a generic projectile.

Effect of the firing position on aiming error and probability of hit

Sources of dispersions that contribute to delivery error and reduce the soldier performance in terms of hit probability are numerous.In order to improve the warfighter performance,the source of the errors contributing to the inaccuracy and dispersion of the weapon systems must be understood.They include ammunition dispersion error,gun dispersion,aerodynamic jump and the aiming error.The aiming error or gun pointing error is defined as the angle between the gun muzzle at the instant the trigger is pulled and the line of fire that corresponds to the intendent aim point.This is a round-to-round error.In weapons systems that include the rifle,the ammunition,a sight and a gunner,the aiming error was shown to be the single most important source of dispersion for the regular infantryman.In other words,for the general purpose rifle weapon system,the weak link is often the human.In order to verify and quantify this assertion,an experimental investigation was carried out to determine the aiming error associated with general purpose rifle fired by infantryman.The aiming error was evaluated for various firing positions and scenarios using infantryman for ranges varying between 100 m and 500 m.The results show that the aiming error is the main contributor to dispersion for the general purpose rifle fired by a non-specialized infantryman.The aiming error induced dispersion for unstressed and rested gunners is shown to be at best equivalent to that of the weapon fired from a bench rest by a marksman.Crown Copyright(?) 2019 Production and hosting by Elsevier B.V.on behalf of China Ordnance Society.