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- Unit System - English or Metric unit operation.
- Drag Model - The drag function used to calculate projectile deceleration,
see the DRAG MODELS section.
- Maximum Flight Time - The projectile flight is calculated using an explicit time
stepping integration routine. This is the maximum simulated flight
time.
- Integration Points Per Second - The number of integration steps per second.
Values as low as 10 seem to produce good data. 1000 was used in
the smallball program, so it is the default here.
The deceleration of a bullet is calculated using standard drag models.
These models were produced by firing a standard projectile at a range
of velocities and recording its performance. The ballistic coefficient
relates any bullet to the standard model. However, only projectiles
shaped exactly the same as the standard will match the model's performance.
For the best accuracy, recalculate the ballistic coefficient of the bullet
using your chosen drag model. Most manufacturers report the B.C. using the
G1 model, so that is the best to start with.
Available Drag Models
- Ingalls - Based on Krupp data of 1881
- British - Based on British 1909 data
- G1 - Standard drag model (similar to Ingalls)
- G5 - Moderate boat tails - 7 degree 30' tail taper with 6.19 caliber tangent nose ogive.
- G6 - Flat base, spire points. 6.09 caliber secant nose ogive
- G7 - "VLD" boat tail. Long 7 degree 30' tail taper with 10 caliber tangent nose ogive.
For .22LR use the G1 model. The G1 is good for blunt nose,
exposed lead bullets with a velocity less than 1400 ft/s.
I have included a datafile of bullets which was taken from PCB by
Odd Harvard Skevik.
www.stud.ntnu.no/~oddske/ballistikk.html
This file will be copied into the share directory.
The first two lines of this file are skipped. For bullet entries,
the diameter and description must end at column 40 and are followed
by the weight and the ballistic coefficient. Feel free to add additional
entries to this file, following the existing format.
- Ballistic Coefficient - Projectile ballistic coefficient.
- Bullet Weight - Projectile weight in grams or grains.
- Wind Velocity - Wind velocity at a 90 degree angle to projectile flight.
- Muzzle Velocity - Initial velocity of projectile.
- Bore-Sight Distance - Distance between the line of sight and the bore.
- Zero Distance - Sight zero distance.
- Firing Angle - Elevation angle of the shot. The Path output in the
trajectory table is calculated relative to this.
- Starting Range - Starting distance listed in the trajectory output.
- Ending Range - Last distance listed in the trajectory output.
- Step Size - Range increment used for the trajectory output.
- Range - The horizontal distance to the projectile location. For calculations
with a non-zero firing angle, the Path values are given for the range
along the line of sight, not the horizontal distance.
- Velocity - Absolute projectile velocity.
- Energy - Projectile kinetic energy.
- Mom. - Projectile momentum.
- Path - Actual projectile flight path in relation to the line of sight.
- Zero - Projectile flight path for a horizontal, zeroed shot.
- Drop - Amount of drop if the projectile is fired perfectly horizontal.
- Drift - Horizontal drift due to wind.
- Time - Flight time of projectile.
This function calculates the projectile ballistic coefficient based
on the input data and the selected drag model.
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