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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Berger Bullets Announces Launch of a New Ammo Company
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<blockquote data-quote="Michael Courtney" data-source="post: 983520" data-attributes="member: 28191"><p>Some other facts and clarifications:</p><p></p><p>Michael Courtney wrote:</p><p></p><p></p><p></p><p>Bryan replied:</p><p></p><p></p><p></p><p>The Air Force funded the study based on a proposal that pointed out that Bob McCoy's work was limited to sea level data. Certainly he had access to the artillery data you suggest, but in his paper, he is very clear he only used the spark range data:</p><p></p><p>"A large amount of high quality free flight total drag data is available at BRL from the firings of various models through the spark photography ranges."</p><p></p><p>This statement was made in his McDrag paper, and is an important part of the empirical justification for having drag coefficients in the 6 d.o.f. models depend only on velocity (or Mach number) and not on air density or Reynolds number. There are a number of other DoD publications that show that supersonic drag coefficients do generally depends on air density (through their dependence on Reynolds number). </p><p></p><p>Our paper on the independence of drag on air density for small arms projectiles has been through the approvals for public release and peer review process and will appear soon in print. It includes both the experimental results as well as a theoretical analysis of why the air density (thus Reynolds number) effects are small enough to neglect and still yield drag coefficients accurate to 1-2% over the range of air densities encountered in small arms fire. The peer reviewers did not raise any objections to the justifications for the study, the results, or the theoretical analysis. If you can cite papers showing prior work empirically justifying the independence of drag coefficients on air density for small arms projectiles, we would appreciate knowing of them. </p><p></p><p></p><p></p><p>The DoD had a keen interest in developing generally accurate methods and models in ballistics. For models and methods to be general, they need to be tested using a range of projectiles. As it happens, military projectiles have much greater manufacturing variations than most sporting projectiles. We picked the 62 grain Berger Flatbase Varmint bullet because it was the same weight as the M855 and M855A1 projectiles, but offered tighter manufacturing tolerances and greater accuracy. We've tested a number of other varmint bullets of different weights in order to test our methods and models over a range of bullet weights and styles, using bullets of greater uniformity and accuracy than the M855. We further face the challenge that even though the DoD wants and expects their scientists to publish in the peer-reviewed literature, present at conferences, and otherwise be well engaged in the scientific community, DoD guidelines make it much harder to get test results approved for public release that include test results from currently fielded equipment. </p><p></p><p></p><p></p><p>Please cite the ballistics paper on which Joshua Courtney is a co-author, as it would be news to me. Not only is your speculation wrong, your facts are wrong also. The support the Air Force provided for our ballistics work included my salary, the purchase of some equipment, approval of my travel, peer-review of research proposals and scholarly papers, and approval of participation by collaborating Air Force scientists. </p><p></p><p>Neither our small company nor any family members ever received a penny of funding from the Air Force. (They have received funding from the Army and the Navy, but this funding resulted from processes I had little or no role in and certainly would withstand the strictest scrutiny regarding nepotism and undue influence. None of this work directly involved varmint bullets.)</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 983520, member: 28191"] Some other facts and clarifications: Michael Courtney wrote: Bryan replied: The Air Force funded the study based on a proposal that pointed out that Bob McCoy's work was limited to sea level data. Certainly he had access to the artillery data you suggest, but in his paper, he is very clear he only used the spark range data: "A large amount of high quality free flight total drag data is available at BRL from the firings of various models through the spark photography ranges." This statement was made in his McDrag paper, and is an important part of the empirical justification for having drag coefficients in the 6 d.o.f. models depend only on velocity (or Mach number) and not on air density or Reynolds number. There are a number of other DoD publications that show that supersonic drag coefficients do generally depends on air density (through their dependence on Reynolds number). Our paper on the independence of drag on air density for small arms projectiles has been through the approvals for public release and peer review process and will appear soon in print. It includes both the experimental results as well as a theoretical analysis of why the air density (thus Reynolds number) effects are small enough to neglect and still yield drag coefficients accurate to 1-2% over the range of air densities encountered in small arms fire. The peer reviewers did not raise any objections to the justifications for the study, the results, or the theoretical analysis. If you can cite papers showing prior work empirically justifying the independence of drag coefficients on air density for small arms projectiles, we would appreciate knowing of them. The DoD had a keen interest in developing generally accurate methods and models in ballistics. For models and methods to be general, they need to be tested using a range of projectiles. As it happens, military projectiles have much greater manufacturing variations than most sporting projectiles. We picked the 62 grain Berger Flatbase Varmint bullet because it was the same weight as the M855 and M855A1 projectiles, but offered tighter manufacturing tolerances and greater accuracy. We've tested a number of other varmint bullets of different weights in order to test our methods and models over a range of bullet weights and styles, using bullets of greater uniformity and accuracy than the M855. We further face the challenge that even though the DoD wants and expects their scientists to publish in the peer-reviewed literature, present at conferences, and otherwise be well engaged in the scientific community, DoD guidelines make it much harder to get test results approved for public release that include test results from currently fielded equipment. Please cite the ballistics paper on which Joshua Courtney is a co-author, as it would be news to me. Not only is your speculation wrong, your facts are wrong also. The support the Air Force provided for our ballistics work included my salary, the purchase of some equipment, approval of my travel, peer-review of research proposals and scholarly papers, and approval of participation by collaborating Air Force scientists. Neither our small company nor any family members ever received a penny of funding from the Air Force. (They have received funding from the Army and the Navy, but this funding resulted from processes I had little or no role in and certainly would withstand the strictest scrutiny regarding nepotism and undue influence. None of this work directly involved varmint bullets.) [/QUOTE]
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Berger Bullets Announces Launch of a New Ammo Company
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