1. Global Measurement Solutions
Method Validation
Projectile Velocity
Van Zyl Koegelenberg
Global Measurement Solutions

2. External Ballistics Repeatability Problem
Knowing what happens once a round leaves the muzzle
Measuring and duplicating claims
Event occurred, is this possible?
Mathematical conclusions ie Energy of projectile, Retardation, etc
9mm, 10 shots, same batch, same test session
Repeatability Problem
No two projectile will ever perform the same
Each shot is unique
Everything changes during the trajectory
Velocity, Acceleration
Environment ie. Air density, Speed of sound, Temperature
Van Zyl Koegelenberg
Global Measurement Solutions

3. Methods available Chronograph Doppler Radar Low cost Easy to use
Can measure at a specific position, where placed
Close range
Doppler Radar
High Cost
Not easy to use
Can measure velocity at a any position in trajectory
Long range
Both are used, it was needed to verify that the everyday use of chronographs are acceptable
Need to verify between Calibration cycles that the Chrono Graphs are in working order
Van Zyl Koegelenberg
Global Measurement Solutions

4. Chronograph method Principle of operation Projectile Start Stop t0 t1
Known Distance ie 1m
Average Velocity Displayed = Distance/Time = 1/Time
Van Zyl Koegelenberg
Global Measurement Solutions

5. Doppler Radar Technology
Projectile Track
Van Zyl Koegelenberg
Global Measurement Solutions

6. Doppler Radar Technology
Van Zyl Koegelenberg
Global Measurement Solutions

7. Comparisons between Radars
Inter-laboratory comparison / Different products, same model / Different products, different models / Same shots, different operators
Dop A
Dop B
Var m/s
Var%
-0.029
0.00%
870
-0.562
-0.06%
0.082
0.01%
0.433
0.05%
0.121
-0.032
0.231
0.03%
0.465
-0.217
-0.02%
-0.101
-0.01%
865.62
-0.073
-0.14
-0.225
-0.07%
-0.139
-0.04%
302.79
-0.192
-0.034
0.42
0.14%
0.125
0.04%
0.148
-0.038
-0.373
-0.13%
-0.759
-0.26%
Average
SDEV
0.08%
The Average % Variance at -0.01%
We found the method reliable and repeatable
Van Zyl Koegelenberg
Global Measurement Solutions

8. Comparing Methods Velocity displayed Projectile
Velocity obtained on Doppler system
Measured at x meter
Two methods, two technologies, same projectile at same time, same conditions
Van Zyl Koegelenberg
Global Measurement Solutions

9. Using both methods to verify Chronographs
Avg
Avg %
SDEV m/s
SDEV %
Min %
Max %
No of Points
0.08%
0.31%
-1.72%
0.83%
187
Place Chronograph at measured distance
Fire shots
Measure velocity at same distance with Doppler
Collecting all information from all tests from all products
Avg
Avg %
SDEV m/s
SDEV %
Min %
Max %
No of Points
0.03%
0.43%
-1.72%
2.67%
801
Done for this presentation
The specified accuracy of the Chronographs are 0.5%
Van Zyl Koegelenberg
Global Measurement Solutions

10. Practical conclusion
8 Joules of energy is treated as a “Licence” or control is required
Research show that ie 8 Joules is required to penetrate the skin, so 8J the critical level
Eye ball can be removed with 12 Joules, etc etc
Hence accuracy is required at all times
Need to prove that the methods used are accurate and repeatable
Suppliers of Forensic products protect their technologies with limited available information
Look at results from practical angle
𝐸𝑛𝑒𝑟𝑔𝑦 𝐾𝑖𝑛𝑒𝑡𝑖𝑐 = 1 2 ×𝑚𝑎𝑠𝑠 × 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 2 =0.5×𝑚 ×
Average measured variance on velocity is m/s
On a 115 grain (7.45g) 9mm round, that is mJ
The specified accuracy of the Chronographs are 0.5%
We found both methods repeatable
We found the chronographs within specifications for everyday use
Chronographs are now verified at least once every 3 months, more work required on the stats
Van Zyl Koegelenberg
Global Measurement Solutions

11. Thank you Conclusion Validated Doppler Technology
Validated Chrono Graph
Utilising both methods in gaining trust as a repeatable solution
Use the test data elsewhere ie. Trajectory prediction
Thank you
Van Zyl Koegelenberg
Global Measurement Solutions