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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Hornady 4DOF Ballistic Program
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<blockquote data-quote="Bullseye" data-source="post: 1227631" data-attributes="member: 3351"><p>"The Hornady® 4DOF™ calculator provides trajectory solutions based on projectile Drag Coefficient (not ballistic coefficient) along with the exact physical modelling of the projectile and its mass and aerodynamic properties. Additionally, it is the first publicly available program that will CORRECTLY calculate the vertical shift a bullet experiences as it encounters a crosswind; referred to as aerodynamic jump." </p><p>The equations of motion based calculation for aerodynamic jump requires the use of aerodynamic coefficients such as Normal Force, Axial Force, Pitching Moment, inertial properties, and more. A modified point mass solver with a minimum of 4 Degrees of Freedom is required to use these coefficients in the equation of motion based correct calculation of aerodynamic jump. </p><p>The proper calculation of spin drift also requires many of the same aerodynamic coefficients to be used. Current methods employing either empirical shooting data, curve fitting, or baseline equations such as the Miller stability formula ignore certain aspects of the actual physics that cause these phenomena to occur. Although this does not absolutely speak to the accuracy of prediction of these alternate methods, Hornady did not write the book on the calculations used in the 4DOF. This work was done more than 50 years ago by names such as Robert McCoy, Bob Whyte, and Wayne Hathaway to name a few. The 4DOF is the first to offer a publicly available, free of charge, solver to correctly calculate aerodynamic jump, and spin drift based on the equations of motion in combination with drag calculations based on actual Doppler measured TOTAL DRAG (Cd vs Mach) for each specific projectile. </p><p>Hornady does gather these aerodynamic coefficients from PRODAS models of the specific projectile. PRODAS gathers these coefficients in a way similar to that of how BC compares a specific bullets drag to a standard. Unlike BC though, a large database of spark range data is used to compare unique features of the projectile being modeled to measured aerodynamic coefficients of spark range tested projectiles. It should be noted, that the predictive abilities of PRODAS were updated in 2004 and are within the error of the spark range measured data for their respective coefficients.</p></blockquote><p></p>
[QUOTE="Bullseye, post: 1227631, member: 3351"] “The Hornady® 4DOF™ calculator provides trajectory solutions based on projectile Drag Coefficient (not ballistic coefficient) along with the exact physical modelling of the projectile and its mass and aerodynamic properties. Additionally, it is the first publicly available program that will CORRECTLY calculate the vertical shift a bullet experiences as it encounters a crosswind; referred to as aerodynamic jump.” The equations of motion based calculation for aerodynamic jump requires the use of aerodynamic coefficients such as Normal Force, Axial Force, Pitching Moment, inertial properties, and more. A modified point mass solver with a minimum of 4 Degrees of Freedom is required to use these coefficients in the equation of motion based correct calculation of aerodynamic jump. The proper calculation of spin drift also requires many of the same aerodynamic coefficients to be used. Current methods employing either empirical shooting data, curve fitting, or baseline equations such as the Miller stability formula ignore certain aspects of the actual physics that cause these phenomena to occur. Although this does not absolutely speak to the accuracy of prediction of these alternate methods, Hornady did not write the book on the calculations used in the 4DOF. This work was done more than 50 years ago by names such as Robert McCoy, Bob Whyte, and Wayne Hathaway to name a few. The 4DOF is the first to offer a publicly available, free of charge, solver to correctly calculate aerodynamic jump, and spin drift based on the equations of motion in combination with drag calculations based on actual Doppler measured TOTAL DRAG (Cd vs Mach) for each specific projectile. Hornady does gather these aerodynamic coefficients from PRODAS models of the specific projectile. PRODAS gathers these coefficients in a way similar to that of how BC compares a specific bullets drag to a standard. Unlike BC though, a large database of spark range data is used to compare unique features of the projectile being modeled to measured aerodynamic coefficients of spark range tested projectiles. It should be noted, that the predictive abilities of PRODAS were updated in 2004 and are within the error of the spark range measured data for their respective coefficients. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Hornady 4DOF Ballistic Program
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