(all these variables have an effect on the drag performance of a projectile). Axial Form Factor:Īllows the shooter to adjust the average Drag Coefficient (Cd) curve for each projectile listed in the calculator, higher or lower, to match his/her specific barrel, propellant, twist rate, rifling, muzzle brake, etc. In inches or centimeters per turn, depending on which units have been selected.
Rather than assuming a fixed atmospheric condition, the calculator calculates an altitude-based atmosphere dependent on the input conditions and allows for the atmosphere to change in air density as the projectile climbs or descends along its line of flight. NOTE: It is necessary with the Hornady 4DOF ® Ballistic Calculator to specify the altitude and atmospheric conditions (either known from a pressure at altitude table or attained from a Kestrel™ or similar device) at the firing location in order for the calculator to accurately predict trajectories. NOTE: This is station pressure, from a Kestrel™ or similar – use of National Weather Service data for the area will not be accurate nor is it recommended for use. Input the elevation at the firing location in either feet or meters above sea level. Wind relative to the projectile headwind = 0 degrees, from the right = 90 degrees, from the left = 270 degrees, etc. Line of sight angle relative to level ground. (A simple web search will reveal several websites that cover this subject in detail.) Shooting Angle: Again, be as precise as possible in order to get the best results. Sight Height:Įxact height of the CENTER of the scope to the CENTER of the bore of the rifle. After running 4DOF ® for a known zero distance and atmospheric conditions, Zero Angle can be input rather than Zero Range and 4DOF ® will output what the trajectory is and the distance zero crossing no matter what the atmospheric conditions or altitude. This will automatically be computed and displayed in the 4DOF ® output as Zero Angle. Be as precise as possible in order to get the best results. Zero Range:Įxact distance from muzzle to target where the rifle was zeroed. The calculator allows a range interval as small as 1 yard or 1 meter. trajectory information for 100, 150, 200 yds would be an interval of 50. The furthest distance you want to be represented in your trajectory output. Muzzle Velocity:Īctual muzzle velocity corrected to the muzzle from the chronograph location. For more details please consult the Hornady® 4DOF ® Ballistic Calculator Technical Document.
The 4DOF ® will now automatically compensate for the performance difference between the known baseline muzzle velocity and the conditions that exist at the time of firing. This known muzzle velocity is also the velocity that should be input in the Muzzle Velocity required below. The Baseline Temperature is the temperature at which a known muzzle velocity was produced. Either input will also ask for a Baseline Temperature. If selected the input allows the use of a Selected Powder TSF or a Custom TSF. This is an optional input and does not have to be used. This option allows 4DOF ® to compensate for changes in muzzle velocity because of temperature changes. You DO NOT specify a BC (this calculator uses a Drag Coefficient and doesn’t use BC). When you do this you are picking a file that contains all the projectile specific information needed to run the 4DOF ® simulation. Pick a projectile from the projectile library. Standard units are SAE units (inches, yards, etc.)Ĭhoose from MOA (Minutes Of Angle, this is true moa 1.047” at 100 yards), MRADS (Milliradians), Inches or Centimeters.Before you begin, the inputs you must have at your disposal include:Ĭhoose from either Standard or Metric (affects ALL inputs and outputs). The essential gun-related inputs are explained below.
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