The purpose of this study is to investigate and quantify some possible sources of dispersion of 120 mm APFSDS tank ammunition both experimentally and numerically.This paper aims to point out the most influential source during In-Bore Balloting Motion phase as well as in External Ballistics phase of the ammunition and quantifies its effect on dispersion.Data obtained from flight trials is critically analysed and parameters affecting dispersion such as initial yaw/pitch rates,yaw/pitch dampening,plane start angle,launch spin,clearance,centre of gravity shift,dynamic imbalance angle,cross wind,etc.are observed and,later on,studied in detail by extensive External Ballistics Monte Carlo(EBMC)simulation and Six Degree of Freedom(6-DOF)trajectory analysis.In Bore Balloting Motion simulation shows that reduction in residual spin by about 5%results in drastic56%reduction in first maximum yaw.A correlation between first maximum yaw and residual spin is observed.Results of data analysis are used in design modification for existing ammunition.Number of designs are evaluated numerically before freezing five designs for further soundings.These designs are critically assessed in terms of their comparative performance during In-bore travel&external ballistics phase.Results are validated by free flight trials for the finalised design. The purpose of this study is to investigate and quantify some possible sources of dispersion of 120 mm APFSDS tank ammunition both experimentally and numerically. This paper aims to point out the most influential source during In-Bore Balloting Motion Phase as well as in External Ballistics Phase of the ammunition and quantifies its effect on dispersion. Data obtained from flight trials is critically analyzed and parameters affecting dispersion such as initial yaw / pitch rates, yaw / pitch dampening, plane start angle, launch spin, clearance, center of gravity shift, dynamic imbalance angle, cross wind, etc. are observed and, later on, studied in detail by extensive External Ballistics Monte Carlo (EBMC) simulation and Six Degree of Freedom (6-DOF) trajectory analysis. In Bore Balloting Motion simulation shows that reduction in residual spin by about 5% results in drastic56% reduction in first maximum yaw. A correlation between first maximum yaw and residual spin is observed. Results of data analysis are used in design modification for existing ammunition. Number of designs are evaluated numerically before freezing five designs for further soundings. These designs are critically assessed in terms of their comparative performance during In-bore travel & external ballistics phase. Results are validated by free flight trials for the finalized design.