JBM Small Arms Ballistics
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A new topic, Elevation, has been added. It shows the differences in trajectories when zeroing at different atmospheric conditions and how to calculate a trajectory for different atmospheric conditions.


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JBM - Calculations - MPM Input

This program calculates a Modified Point Mass trajectory. It is done by using an approximation for the yaw of repose to simplify the 6DOF (Six Degree of Freedom) equations. It provides estimates of spin drift and magnus effects. Explanation of terms.

Caliber (0.1-2.0 inches) [0.308]
Nose Length (1.2-5.5 calibers) [2.260]
Meplat Diameter (<0.35 calibers) [0.250]
Ogive Radius (1-1000 calibers) [7.0]
Drag Function [G1]
Boattail Length (<2 calibers) [0.510]
Base Diameter (<1 caliber) [0.7662]
Total Length (2.5-10 calibers) [3.980]
Rotating Band Diameter (1.0-1.06 calibers) [1.000]
Core Depth (0.0-2.0 calibers) [0.256]
Jacket Thickness (0.0-0.500 Calibers) [0.091]
Jacket Length (0.0-10.0 Calibers) [3.980]
Weight (10-15000 grains) [168]
Boundary Layer [Laminar-Turbulent]
Jacket Specific Gravity (5.0-20.0) [8.9]
Core Specific Gravity (5.0-20.0) [11.5]
Axial Moment of Inertia (0.00001-0.1) [0.000247]
Transverse Moment of Inertia (0.0001-0.1) [0.001838]
Center of Gravity (0.1-10.0 calibers) [2.44]
Muzzle Velocity (500-4500 ft/sec) [2600.0]
Chronograph Distance (0-100 feet) [0.0]
Sight Height (0-100 inches) [1.5]
Sight Offset (-100-100 inches) [0.0]
Zero Height (-100-100 inches) [0.0]
Zero Offset (-100-100 inches) [0.0]
Azimuth (-300-300 MOA) [0.0]
Elevation (-300-300 MOA) [0.0]
LOS Angle (-90-90 degrees) [0.0]
Cant Angle (-90-90 degrees) [0.0]
Direction (0-360 degrees) [0.0]
Latitude (-90-90 degrees) [0.0]
Altitude (-1000-15000 feet) [0]
Vital Zone Radius (3.0 - 20.0 inches) [5.0]
Barrel Twist (2.0-100.0) [12.0]
Twist Direction [Right]
Wind Speed (-100-100 mph) [10.0]
Wind Angle (0-360 deg) [90]
Minimum Range (0-1999) [0]
Maximum Range (1-3000) [1000]
Range Increment (1-2000) [100]
Zero Range (1-2000) [100]
Temperature (-40-140 °F) [59]
Pressure (15-40 inches Hg) [29.92]
Relative Humidity (0-100%) [0]
Drop Units (First Column)
Drop Units (Second Column)
Ranges in Meters Drop and Windage Relative to Target
Elevation Correction for Zero Range Azimuth Correction for Zero Range
Standard Atmosphere at Altitude
Include Coriolis Effects Include Aerodynamic Jump
Include Magnus Effects Include Coefficients
Include Trajectory Calculate Inertia
Calculate Center of Gravity SPINNER CMα
SPINNER CLα SPINNER CLp
Geometry Correction

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JBM Small Arms Ballistics. Last update 15 July 2008, Copyright © 1996-2008 JBM [V]