April 13th, 2020

Barnes Bullet Ballistics Determined with Doppler Radar Testing

Ballistics Barnes Bullets Doppler Radar G1 G7 curve model drop chart DOF 6 degree of freedom

NOTE: Barnes has just opened a new e-Commerce site where you can buy Barnes bullets direct from the manufacturer. To mark that development, we’re republishing an interesting article on how Barnes develops BC values and ballistic data for its match bullets and ammunition. Barnes employs advanced Doppler Radar to record bullet speeds at multiple distances out to 1500 yards.

Determining Bullet Ballistics with Doppler Radar Data

How do you build better (more precise) ammo drop tables? With radar, that’s how. Barnes Bullets is using Doppler Radar to develop the drop tables for its Precision Match line of factory ammunition. The Doppler radar allows Barnes to determine actual velocities at hundreds of points along a bullet’s flight path. This provides a more complete view of the ballistics “behavior” of the bullet, particularly at long range. Using Doppler radar, Barnes has learned that neither the G1 nor G7 BC models are perfect. Barnes essentially builds a custom drag curve for each bullet using Doppler radar findings.

Use of Doppler Radar to Generate Trajectory Solutions

by Barnes Bullets, LLC
Typical trajectory tables are generated by measuring only two values: muzzle velocity, and either time-of-flight to a downrange target, or a second downrange velocity. Depending on the test facility where this data is gathered, that downrange target or chronograph may only be 100 to 300 yards from the muzzle. These values are used to calculate the Ballistic Coefficient (BC value) of the bullet, and the BC value is then referenced to a standardized drag curve such as G1 or G7 to generate the trajectory table.

Ballistics Barnes Bullets Doppler Radar G1 G7 curve model drop chart DOF 6 degree of freedomThis approach works reasonably well for the distances encountered in most hunting and target shooting conditions, but breaks down rapidly for long range work. It’s really an archaic approach based on artillery firings conducted in the late 1800s and computational techniques developed before the advent of modern computers.

There is a better approach which has been utilized by modern militaries around the world for many years to generate very precise firing solutions. Due to the sizeable investment required, it has been slow to make its way into the commercial market. This modern approach is to use a Doppler radar system to gather thousands of data points as a bullet flies downrange. This radar data is used to generate a bullet specific drag curve, and then fed into a modern 6 Degree of Freedom (DOF) [ballistics software program] to generate precise firing solutions and greatly increase first-round hit probability. (The 6 DOF software accounts for x, y, and z position along with the bullet’s pitch, yaw, and roll rates.)

Bullet-Specific Drag Curves Derived from Radar Data
Barnes’ advanced Doppler radar system can track bullets out to 1500 meters, recording the velocity and time of flight of that bullet every few feet along the flight path. The noteworthy graph below shows a Doppler Radar-derived, bullet-specific drag curve alongside the more common G1 and G7 curves:

Ballistics Barnes Bullets Doppler Radar G1 G7 curve model drop chart DOF 6 degree of freedom

Neither of the standard curves is a particularly good match to our test bullet. In the legacy approach to generating a downrange trajectory table, the BC value is in effect a multiplier or a fudge factor that’s used to shift the drag curve of the test bullet to try and approximate one of the standard curves. This leads to heated arguments as to which of the standardized drag curves is a better fit, or if multiple BC values should be used to better approximate the standard curve (e.g., use one BC value when the velocity is between Mach 1 and Mach 2, and a different BC value when the velocity is between Mach 2 and Mach 3.) Barnes’ approach to creating trajectory tables is to generate bullet-specific drag curves, and use that data directly in a modern, state-of-the-art, 6 DOF ballistics program called Prodas to generate the firing solution.

Story tip from EdLongrange. We welcome reader submissions.

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