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JBM - Calculations
NOTE: I will not guarantee these calculations for ANY purpose.
Remember to use common sense at all times and to check loading with
current manufacturer's data.
If you think the functionality has changed, check the list of
changes because it probably has!
Ballistic Coefficients (Time)
Calculates the ballistic coefficient for a near velocity,
time of flight, atmospheric conditions and drag function.
Ballistic Coefficients (Velocity)
Calculates the ballistic coefficient for near and far
velocities, atmospheric conditions and drag function.
Bullet Drag and Twist
Calculates the bullet CD, and CD components, BC required twist and
stability for input twist. Inputs required are the bullet measurements
including nose length, total length, boattail length, meplat diameter,
base diameter, caliber, weight, atmospheric conditions and drag function.
This algorithm is based on the McDrag work done by Robert McCoy.
See bibliography
Drag Function Conversion
Converts a ballistic coefficient for one drag function to a ballistic
coefficient for another drag function. Also calculates the sectional
density and form factors.
Maximum Distance
Calculates the maximum range a bullet can travel given the
muzzle velocity, ballistic coefficient, weight and atmospheric
conditions.
Modified Point Mass Trajectory
Calculates a trajectory from bullet dimensions. This type of trajectory
provides a good estimate for things like spin drift and stability.
I have also added coriolis effects. It has a considerable number of
inputs, so beware. This online calculation replaces my previously available
MPM program.
Power Factor
Calculates the power factor and checks divisions for IDPA,
IPSC, TSA and USPSA.
Recoil
Calculates the free recoil energy and velocity using firearm
weight, charge weight, bullet weight and firearm velocity.
Trajectories
from bullet BC and firearm info. Inputs include muzzle velocity,
sight heights, chronograph distance, ballistic coefficient, drag
function, line of sight and cant angles and atmospheric conditions.
Output options include variable ranges and choice of units for windage
and drop (inches, MOA, and mils). Calculations are performed assuming
the bullet is a point mass. Elevation and azimuth are iteratively
corrected to ensure a correct zero.
Trajectories -- Simplified
Many people don't use all the terms in the trajectory calculation page listed
above, so this program uses the default values for inputs not set by the user.
The calculation is done with the same program as the trajectory page
above.
Trajectory Cards
Calculates a "range card" using velocity as a function of temperature,
altitude densities, specific ranges and zero conditions. The output is a matrix
of values for bullet drop and windage as a function of temperature and altitude
density. The two input muzzle velocities and there temperatures are required so
that the program can calculate and accurate muzzle velocity at different temperatures
using linear interpolation. To find these values, chronograph a particular load at
two different temperatures (the farther apart the better).
This calculation finds the firearm elevation at the specified zero
ranges and applies it to the calulated trajectories to show the difference in
bullet drop at shooting conditions different from the zero conditions. For
more information see
this topic.
Trajectory μCards
Calculates a small "range card". Most of the inputs are the same as the large
trajectory card, but it also includes target direction and speed. Cant is not
included, because it makes the target lead pretty complicated (if not useless).
Output includes only the notes that you enter and the table. The table is
similar to the old card -- drop, windage and lead in two units.
This calculation finds the firearm elevation at the specified zero
ranges and applies it to the calulated trajectories to show the difference in
bullet drop at shooting conditions different from the zero conditions. For
more information see
this topic.
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