- Used in estimating the atmospheric conditions. This value is not
used unless the Standard Conditions at Altitude checkbox is checked.
- Axial Moment of Inertia
- The moment of inertia about the centerline axis of the bullet.
- The horizontal (side to side) angle the barrel makes with the
line of sight. This value is not generally known and can be ignored
if the "Azimuth Correction for zero range" option is checked.
- Azimuth Correction
- If checked, the azimuth is changed to make the bullet cross the
line of sight at the zero range -- zero windage at the zero range.
- Barrel Twist
- The twist rate (inches per turn) of the barrel. This value is used
to calculate stability. It should not be confused with the required twist
calculated by Bullet Drag.
- Base Diameter
- The diameter of the base of the bullet. For boattails, this is
smaller than the caliber.
- Boattail Length
- The length of the boattail from the rear of the bearing surface to
the base of the bullet. It is zero for flat base bullets.
- Boundary Layer
- The flow over the bullet at the boundary layer. It can
be entirely laminar (laminar-laminar), laminar then turbulent (laminar-turbulent)
or completely turbulent (turbulent-turbulent). McCoy states that this should
be laminar-turbulent unless you know better (e.g. have pictures of the flow).
- Bullet Weight
- The weight of the bullet.
- Diameter of the bullet's bearing surface (that part that contacts
the rifling of the barrel), measured in inches.
- Cant Angle
- The angle of the tilt of the firearm to the right or left from
vertical. Positive angles are to the right.
- Center of Gravity
- Distance to center of gravity from nose in calibers.
- Chronograph Distance
- The distance from the muzzle of the firearm to the chronograph used
for muzzle velocity measurements. If the muzzle velocity is estimated,
enter 0.0 for this value -- no correction.
- Drop Units 1st Column
- A drop value (the number you enter) and its associated
units. Output windage for the first column are multiples of this value/units
combination. See the drop units topic
for more information.
- Drop Units 2nd Column
- Same as Drop Units 1st but for the second column
of drop, windage and lead.
- Core Depth
- Distance from the tip of the bullet to the top of the lead (or other material) core.
- Core Specific Gravity
- Specific gravity of the bullet core
- Firing direction in degrees. This is the compass direction the firearm is
pointing. North is 0° East is 90°, South 180° and West is 270°.
- Drag Function
- The drag function to use to calculate the ballistic coefficients.
Most commercial bullets use the G1, but for some long range bullets, the G7
or G8 is typically a better choice. Some military bullets fit the G5 and
G6 functions better than the G1. The GL is for high drag bullets and won't
really fit anything that Bullet Drag can calculate coefficients for. GI is
the Ingall's drag function and is thrown in for fun. This value is only
used for calculating the ballistic coefficient.
- The vertical angle the barrel makes with the line of sight.
This value is not generally known and can be ignored if the "Elevation
Correction for zero range" option is checked.
- Elevation Correction
- Or Drop correction, causes the elevation to be raised as required
to cause the bullet to cross the line of sight at the zero range. Without
this box checked, the zero range is ignored.
- Include Aerodynamic Jump
- If checked, the effects of aerodynamic jump (wind at the muzzle)
are included in the trajectory calculation
- Include Coefficients
- If checked, the ballistic coefficients used to calculate the
trajectory are included in the output
- Include Coriolis Effects
- If checked, the coriolis effects are included in the trajectory
- Include Magnus Effects
- If checked, the magnus effects are included in the trajectory
- Jacket Length
- This value is the length of the jacketed portion of the bullet. This will typically
be equal to the length of the bullet, but for those bullets with a lead tip, this
value will be less than the total length. NOTE: if you have a jacket length less
than the total length, the program sets the core depth to zero.
- Jacket Specific Gravity
- Specific gravity of the bullet jacket.
- Jacket Thickness
- The thickness of the jacket.
- Line of Sight Angle
- The angle between the line of sight and level ground. This value
is used when shooting uphill or downhill. Value is a positive angle when shooting uphill
and a negative angle when shooting downhill.
- Maximum Range
- The maximum displayed range.
- Meplat Diameter
- The diameter of the flat portion of the tip of the nose of the bullet.
For some bullets, the meplat diameter is zero (or very close).
- Minimum Range
- The minimum displayed range. Data is calculated from the muzzle
the maximum range, but may be displayed from the minimum to the maximum
range. (e.g. with a minimum of 990, maximum range of 1010 and a range
increment of 10 you would see data 990, 1000, 1010 yards).
- Muzzle Velocity
- The velocity of the bullet as either (1) measured at some distance
from the muzzle or (2) as estimated from reloading data. The on-line
ballistics page can correct for the distance to chronograph. (The velocity
lost traveling to the chronograph.)
- Nose Length
- The length of the nose from the front of the bearing surface to the
- Ogive Radius
- The radius of the nose ogive. For conical bullets, this value is
not used since the ogive radius is essentially infinite.
- Point Mass Trajectory
- This option forces the calculation to use only the drag term
dropping other effects like aerodynamic jump, drift and magnus. The spin rate
and coriolis effects (if checked) are still calculated.
- The barometric pressure. It must be an absolute pressure, not a
corrected station pressure.
- Range Increment
- the increment used in displaying the calculated data.
- Ranges in Meters
- When checked, all ranges entered (minimum, maximum, increment and zero) are in
- Relative Humidity
- Relative humidity (percent)
- Rotating Band Diameter
- The diameter of the rotating band, if any. Most small arms bullets
do not have rotating bands (although the rear of the bearing surface may
be 1/10000's larger than the caliber, Bullet Drag Calculations do consider
this a rotating band) and therefore the rotating band diameter is equal to
- Sight Height
- The height of the sight (or scope) above or below from the centerline
of the barrel. This is required because the bullet starts at a drop of
- Sight Offset
- The offset of the sight (or scope) to the left or right of the
centerline of the barrel.
- SPINNER CLα,
CMα and CLp
- This program has two methods for calculating CLα, CMα
and CLp, GE's SPINNER program or Bob McCoy's INTLIFT and McDrag program. If checked (default),
SPINNER is used, if not, McCoy's INTLIFT and McDrag are used.
- Standard Conditions at Altitude
- When checked, the temperature, pressure and humidity for standard
atmospheric conditions at the entered altitude (always 0% at standard
conditions) are entered in the calculation. The standard used is the ICAO
- The measured or estimated air temperature.
- Total Length
- The total length of the bullet from the base to the meplat.
- Transverse Moment of Inertia
- The moment of inertia about an axis perpendicular to the bullet
centerline, through the center of gravity.
- Twist Direction
- The direction of barrel twist when looking down the barrel from the chamber to the muzzle.
A clockwise twist it "Right", a counterclockwise twist is "Left".
- Vital Zone Radius
- Radius of the vital zone for which the maximum point blank
range is calculated. The vital zone is defined as the area from one radius below
the line of sight to one radius above the line of sight.
- Wind Angle
- Angle of the wind direction. A North wind has an angle of zero,
an East wind, 90 degrees, a South wind 180 and a West wind of 270 degrees.
- Wind Speed
- The speed of the wind.
- Zero Height
- The height of the zero point at the zero range.
- Zero Offset
- The lateral displacement the zero point at the zero range.
- Zero Range
- The range at which you wish the bullet to cross the line of sight.
- Atmospheric Density
- The calculated density of the air.
- The angle that the barrel makes with the line of sight in a
horizontal direction -- positive to the shooter's right. This is the
"lead" angle in minutes of angle for the selected zero range.
- The ballistic coefficient calculated using the drag function you
- Drag coefficient.
- Drag coefficient, second derivative.
- Lift coefficient
- Spin damping moment coefficient
- Pitching moment coefficient.
- Magnus force coefficient
- Magnus moment coefficient
- The distance above or below the line of sight. Listed in either
inches, minutes of angle or mils (6400 mils per 360 degrees or 3.375 mils
per MOA). Drop is positive above the line of sight and negative below the
line of sight.
- The angle that the barrel makes with the line of sight in a vertical
direction. This is the "holdover" angle in minutes of angle for the
selected zero range.
- Kinetic energy of the bullet. The kinetic energy is
a measure of the maximum amount of work (force time distance) an object
can do. [It is also a measure of the work done by the firearm/case/primer/powder
on the bullet.]
- The form factor for the bullet. This is a ratio of the actual CD
of the bullet to that of the CD of the "standard" bullet for the selected
- Mach Number
- Mach number for the given velocity and atmospheric conditions.
- Maximum Point Blank Range
- Maximum range for which the bullet does not go above or below the
maximum point blank range radius.
- Maximum Point Blank Range Zero
- Zero range to achieve the maximum point blank range.
- Distance from the shooter along the line of sight.
- Range at Max. Height
- This is the range at which the bullet reaches its maximum
height in the vital zone when doing the maximum point blank range calculation. This
is NOT the maximum height of the bullet for the trajectory calculation.
- Sectional Density
- Bullet sectional density
- Stability factor for the bullet at the given velocity/range. It
should be greater than 1.0 to ensure stability.
- Speed of Sound
- The calculated speed of sound.
- The time of flight of bullet in seconds.
- The speed of the bullet in feet per second.
- The distance to the right or left of the line of sight. Windage
is positive to the shooters right and negative to the shooters left.