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One of the features that sets JBallistics apart from most other ballistics programs is its implementation of the Modified Point Mass
Model. This model allows the calculation of bullet drift due to spin effects. This model is also more accurate for trajectories
evaluated at longer ranges and higher angles of fire. This screen shows additional results parameters that can be plotted after
a modified point mass analysis. Shown is bullet spin rate versus distance, bullet drop (height) versus distance for a high angle of fire
all the way until the bullet hits the ground, a bullet stability factor giving an indication if the bullet is travelling normally or
is tumbling, and the quasi steady-state yaw of repose indicating the amount of drift-producing yaw experienced by the bullet.
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This plot shows the amount of drift off-course the bullet will produce. Drift can be due to a cross wind, Coriolis effects, and spin drift.
If you specify no cross wind and turn off Coriolis effects, spin drift is all that is left. Spin drift is only computed when using the
Modified Point Mass Model. Bullet spin drift at long ranges can be quite substantial.
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JBallistics can compute custom drag functions for a bullet based on its shape parameters. Rather than depend on the selection of a standard 'G'
function and a ballistic coefficient which relates the performance of your bullet to a standard projectile, you may specify the shape of a
bullet and JBallistics will use advanced algorithms to produce a custom drag function for that bullet. This may be used with either the Point Mass
or Modified Point Mass Model. JBallistics also provides a graphical utility tool to assist with the determination of these shape parameters.
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For those instances where you have access to experimentally obtained aerodynamic coefficient data which may be more accurate than the
algorithmically computed data JBallistics can provide, you may enter the values in a table for storage into the database. You may have one
set of these for each custom drag function you define. Tell JBallistics to use the table rather than calculated coefficients and these will
be used in the trajectory calculation. You may specify as a function of mach number the best you can for: the drag function, yaw drag
function, lift coefficient, spin damping moment coefficient, linear pitching (overturning) moment coefficient, cubic pitching (overturning)
moment coefficient, and the magnus force coefficient. Aerodynamic coefficient data is provided in the database for the Sierra
International .308 bullet.
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