Reloading 202 – Rifle Zero and Ballistic Solvers

The following information is for those engaging targets and/or animals at ranges far beyond what until relatively recently was considered consistently achievable.

As you stretch out to engage targets at 1000, 1500, 2000, 2500, 3000 yards it becomes critical to have precise inputs for your ballistic solver, and set a highly precise zero angle (not zero distance) for your rifle.

You are also stepping beyond the capabilities of traditional Ballistic Coefficient based ballistic solvers which take a limited number of inputs and base their calculations on a standard bullet profile which doesn’t sufficiently match the projectile you are using.

For a ballistic solver to return the correct dial up at long ranges it requires more input parameters than a BC based calculator, in conjunction with high resolution in-flight data for the actual projectile you are using.  An example of such a solver is Hornady’s 4DOF, which utilises doppler radar acquired data for several bullet manufacturer’s projectiles including its own.

What are the issues with setting a zero distance and using BC based solvers at very long ranges?

  • a rifle’s zero distance changes with local environmental conditions.  If you’ve zeroed for 100 yards, in different conditions your zero distance will be less than or more than 100 yards.  This leads to errors that amplify at longer distances. Shooters using zero distance will often re-zero their rifle at a shooting venue prior to a match to align their zero distance with local environmental conditions.
  • A BC based solver cannot provide sufficiently precise dial ups at longer distances.  As you push the range out the error exceeds the size of the target and you will consistently miss.  Shooters will then lie to the solver by changing inputs such as BC or muzzle velocity to get the rounds on target at that particular distance.  These lies need to be repeated at each distance engaged.

How do we address the above issues?

  • use a solver that uses zero angle.  This is the angle between your scope and bore, and unless you fiddle with your rifle system never changes.
  • use a solver that has a highly accurate model of your projectile’s trajectory.

In conjunction with environmental inputs, an accurate muzzle velocity, and several other inputs your solver will now give you a precise scope dial up.

Can you say “First round hits on target”?





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