- Used in estimating the atmospheric conditions. This value is not
used unless the "Standard Conditions at Altitude" checkbox or the "Pressure is Corrected"
checkbox is checked.
- Ballistic Coefficient
- The ballistic coefficient for the bullet being used. It is almost
always obtained from the manufacturer, but can also be measured. The
ballistic coefficient is represents the ratio of the drag of the standard
(e.g. G1 standard bullet) bullet to that of the bullet you are shooting.
A ballistic coefficient of 0.100 means that your bullet has 10 times the
drag of the standard bullet.
- Barrel Twist
- The twist length of the barrel.
- Twist Direction
- The twist direction of the barrel. Right is a
clockwise twist when looking through the barrel from the chamber to the
muzzle. Left is counter-clockwise.
- Bullet Length
- The length of the bullet. When using a bullet in the library,
this value is only used if the library value for length is zero (unknown).
- Bullet Library
- A drop down list showing all the buttons in the library. If
a bullet is selected, the trajectory is run with the selected bullet. If
"None (Use entered BC)" is selected, the entered BC, drag function and weight are used.
Lapua bullets with "(CD)" in the description use the Drag Coefficients supplied by
Lapua instead of the ballistic coefficient. Bullets with "(Litz)" in the description
use Bryan Litz' BCs.
- Bullet Weight
- The weight of the bullet.
- Diameter of the bullet.
- Cant Angle
- The angle of the tilt of the firearm to the right or left from
vertical. Positive angles are to the right.
- Distance to Chronograph
- 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.
- Drag Function
- A drag function (or G function) provides the forces on a standard
bullet for which the drag function was derived. A bullet's ballistic
coefficient then relates the drag on any bullet to that of the standard
- 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.
- 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 for Zero Range
- 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.
- "Energy Column" Formula
- Use this input to select what is calculated for "energy" column
(fourth column from the right). Values include Energy in foot-pounds or Joules, momentum
in pound-seconds or Newton-seconds, Taylor's Knockout Value, optimum game weight for
hunting or varmint bullets and Krupp's tank formula in inches and millimeters. Krupp's
tank formula gives the thickness of a sheet of mild construction steel that can be
penetrated by a full metal jacketed, lead core round. It does not calculate the
the penetration depth into a solid (semi infinite) block of steel.
- Relative humidity (percent)
- Include Danger Space
- If checked, the output will include the danger space
for every calculated range.
- Include Extra Rows
- If checked, the output will include extra rows even if
they are not an multiple of the range increment. Extra possible rows include
the sound barrier crossing, zero range and maximum point blank range.
- Include Spin Drift
- If checked, the Litz spin drift is calculated for each range.
The bullet length must be entered (even if you are using a bullet in the library)
to calculate spin drift.
- 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.
- Mark Sound Barrier Crossing
- If checked, the output velocity background color is red
for the first printed velocity that is less than the calculated speed of sound.
- Maximum Range
- The maximum displayed range.
- 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.)
- Plastic Tip Length
- The length of the plastic tip (e.g. "Ballistic Tip").
If the bullet has no plastic tip, enter zero. This value is used to implement the
second version of the Miller Stability rule.
- The barometric pressure. It may be corrected or uncorrected
depending on the state of the "Corrected Pressure" checkbox.
- Pressure is Corrected
- Check this box if the pressure entered is a corrected station
pressure. If it is an absolute pressure, leave this unchecked.
- 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 meters.
- Round Output to Whole Numbers
- Removes any part of the drop, windage or lead after the decimal point.
This is useful when your drops match the scope click settings and you want the output to be
in number of clicks.
- 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. Positive offsets are to the shooter's right. Negative
- Std Atmosphere 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
- Target Angle
- The angle of the target speed direction with the line of sight.
A 90 degree angle is a target moving perpendicular to the line of sight.
This angle is given in degrees by selecting an angle from the list.
- Target Height
- The height of the target. This value is used in calculating
the danger space.
- Target Relative Drops
- Calculates the bullet drop relative to the target and not the line
of sight. These values are only different when the cant angle is non-zero.
- Target Speed
- The speed of the target in miles per hour. This value is used to
calculate running target leads. Negative speeds are to the shooters left,
positive to the shooter's right.
- The measured or estimated air temperature.
- 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.
- 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 "Windage Correction for zero range" option is checked.
- Windage Correction for Zero Range
- If checked, the windage is changed to make the bullet cross the
line of sight at the zero range -- zero windage at the zero range.
- Wind Angle
- Angle of the wind direction. A wind blowing downrange has an angle of zero,
a wind blowing to the shooter's right has an angle of 90, a headwind, an angle
of 180 and a wind blowing to the shooter's left has an angle of 270 degrees.
- Wind Speed
- The speed of the wind.
- Zero at Max. Point Blank Range
- If checked, the zero range is changed to achieve the maximum
point blank range.
- 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.
- Danger Space
- The minimum and maximum range near the output range for which the
bullet will hit a target of the entered height. This is used as an gauge of the
required range estimation accuracy.
- 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 required target lead to the left or right of the line of site to
hit a moving target. Lead is positive to the shooter's right and negative to
the shooter's left.
- 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
- Speed of Sound
- The calculated speed of sound.
- An approximated value of the bullet stability at the muzzle.
This value should be greater than 1.5 (Don Miller says value should be 1.3 to 2.0).
Values less than 1.0 are dynamically unstable and will tumble.
- 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.