The Effect of Statistical Velocity Variation on the Gaussian Bivariate Probability of Hit for Small Caliber Systems.

摘要

The statistical variations in both the average velocity and the linear standard deviation of velocity, due to the location of propellant airspace, are investigated by trajectory conversions to errors on a vertical target and by calculations of rectangular hit probabilities with the Gaussian bivariate distribution. The two cartridges examined are the 7.62mm, Ball, M80 and the 5.56mm, Ball, M193. Sources of errors and their magnitudes are discussed. Two diverse levels of aiming error are assumed, corresponding to present requirements for the Future Rifle System. The range-dependent errors due to velocity variations are treated as perturbations of the ballistic error. The nose-tap (NT) procedure of chambering cartridges is compared to the standard base-tap (BT) procedure by assuming that zero bias is applicable to the BT procedure and that the NT procedure introduces a finite bias. Calculations are conducted with assumptions which tend to maximize the influence of the velocity variation, and the limiting case of zero aiming error is also treated. The changes in hit probability due to the statistical velocity variations corresponding to the BT and NT air space positions are shown to be insignificant for these two standard cartridges. (Author)