Listed below are the supersonic averaged G1 and G7 Ballistic Coefficients for the seven bullets used during the 338 bullet demonstration held on December 10th, 2011 in Nevada. The bullets are listed below in the random order in which they were tested.
Bullet 1: 300gr Sierra MatchKing – Manufacturer reported BC – 0.759 averaged G1 Acoustically determined BC – 0.747 G1 and 0.380 G7
Bullet 2: 285 gr Hornady BTHP Match – Manufacturer reported BC – 0.720 averaged G1 Acoustically determined BC – 0.685 G1 and 0.348 G7
Bullet 3: 245 gr Lehigh turned solid Acoustically determined BC – 0.651 G1 and 0.333 G7
Bullet 4 – 232 gr GS Customs SP turned solid – Manufacturer reported BC – 0.686 averaged G1 Acoustically determined BC – 0.578 G1 and 0.298 G7
Bullet 5 – 235 gr Predator turned solid Acoustically determined BC – 0.556 G1 and 0.282 G7
Bullet 6 – 300 gr Berger Hybrid (Gen II) – Manufacturer reported BC – 0.816 G1 / 0.418 G7 Acoustically determined BC – 0.766 G1 and 0.389 G7
Bullet 7 – 276 gr ZA turned solid – Manufacturer reported BC – High Acoustically determined BC – 0.719 G1 and 0.362 G7
For more details about the acoustic chronograph and BC discussions see the following pages.
Rounds ready for testing
Acoustic Chronograph Details
The basic idea of the entire test procedure is to use acoustic sensors to measure the bullet’s time of flight to various distances. Each bullet fired has the muzzle velocity measured with a chronograph and then passes over microphones placed at four downrange distances. Due to the types of bullets tested and terrain of the test facility, microphones for this test were placed at 313 yards, 487 yards, 1093 yards, and 1264 yards. The raw data for each shot is in the form of a sound file which shows spikes when the bullet passes over the microphone. Also during each shot, the atmospherics are carefully monitored using a Kestrel 4500. After all the test rounds were fired, the post processing of the sound traces begins by using custom written computer programs in conjunction with a custom written ballistic calculator. After the time of flight for each round fired has been calculated from the data traces; this flight time, atmospheric conditions, and muzzle velocity are entered into the pre-processor for the ballistic calculator where the drag of the projectile is varied until the calculated flight time conforms to a best fit match of the experimentally observed time of flight. This process is repeated for each individual projectile that was fired during the test. This process allows you to determine the unique shape of the drag curve for each bullet.
For this test, the results are presented as ballistic coefficients averaged over the supersonic realm of the bullet. Since we are using acoustic sensors, it is impossible to determine the ballistic coefficient of any bullet when it is subsonic. We also did not test for subsonic transition stability due to safety reasons. Further post processing of the acoustic data can result in velocity banded ballistic coefficients is possible, but as of yet has not performed on the data from this demonstration.
Discussion of Acoustically Determined Ballistic Coefficients
Many shooters are aware that Bryan Litz has previously developed his own proprietary acoustic chronograph and has published two books containing acoustically tested ballistic coefficients of many different bullets. Mr. Litz has tested some of the same bullets that were used during this test, and published the data in one or both editions of his book, Applied Ballistics for Long Range Shooting. We are pleased to acknowledge that a substantial portion of our data correlates with the Litz data to within acceptable experimental errors. Mr. Litz published that the averaged G1/G7 of the 300 gr SMK is 0.745/0.381, while our test calculated a averaged BC of 0.747/0.380. Another bullet tested during this demonstration and by Mr. Litz is the 285 gr Hornady BHTP match bullet. Mr. Litz reports an averaged G1/G7 BC of 0.699/0.358. Our test determined an averaged G1/G7 BC of 0.685/0.348, a difference of only 2%. Another common bullet to both tests is the GS Customs 232 gr SP solid lathe turned monolithic solid. Mr. Litz reported an averaged G1/G7 BC of 0.604/0.309, while our test data produced an averaged BC of 0.578/0.298, a difference of 3.5%. These results show that both the method used by Mr. Litz and the method used during this test are equivalent.
There is a notable disparity between the reported ballistic coefficient(s) for the Berger 300gr Hybrid Generation II projectiles. This caused some consternation as the other data that can be compared to Mr. Litz’s tests shows very good correlation. As a result of that disparity the data has been checked 3 distinct times to look for any human error during post processing (with none found). Perhaps at some later date Mr. Litz and KnS Ballistic Services will have the opportunity to discuss the issue at length and endeavor to explain the anomalies noted.
The raw data files and details necessary to process the flight times are available to each of the respective manufacturers upon reciep of written request. We will not distribute the raw data traces other than to respective manufacturers and/or their authorized representatives.
KnS Ballistic Services would like to extend a big thank you to Mr. Galli of Sniper’s Hide, Mr. Trapp of Gunsite Academy, Mr. VanNiel who independently supported this test and was instrumental to the coordination effort with KnS Ballistic Services and Sniper’s Hide to get this demonstration moving. Thank you to the Sniper’s Hide members and sponsors (specifically SouthWest Ammunition and Zethilius Assoc) for the generous donations of projectiles and loaded ammunition. A number of other supporters took time from their weekend to come out and assist with setup, logistics, and break down of the test. Without all of the endeavors of everyone, this would have been an impossible undertaking. We look forward to future testing and offer our assistance and services whenever necessary.
KnS Ballistic Services, LLC.