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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: 983029" data-attributes="member: 28191"><p>Notes on Weapon Employment Zone Analysis of Berger 230 grain Tactical Match Hybrid in XM-2010 Rifle</p><p></p><p>The analysis Bryan Litz published made two key assumptions in comparing the Berger 230 grain Tactical Match Hybrid with the 220 SMK load in his analysis. </p><p></p><p>The fist assumption was that the 230 grain bullet could be pushed to 2900 fps in a 26" barrel and 2800 fps in the 24" barrel of the XM-2010. As it turns out the AMB published spec is 2850 fps in a 26" barrel which probably yields closer to 2750 fps in the 24" barrel of the XM-2010.</p><p></p><p>The second assumption was that the 230 grain bullet would yield a G7 BC of 0.380 at sea level conditions in the 1 in 10" twist of the XM-2010 rifle. Since this was published in 2012 Bryan has revised his understanding of how stability impacts ballistic coefficient and his new stability calculator gives a G7BC of 0.361 at sea level conditions with a 1 in 10" twist. The calculator recommends a 9.25" twist for to achieve the full rated BC of this bullet.</p><p></p><p>These factors will undoubtedly combine to reduce the gap between the 220 SMK and the 230 Target Match Hybrid in the WEZ analysis. </p><p></p><p>One may further consider that our independent measurements of Berger ballistic coefficients has consistently yielded BCs 8% to 15% below Berger's published values. If the published BC of this bullet is also overly optimistic by 8% to 15%, the performance gap between the 220 SMK and the 230 Target Match Hybrid will be reduced even further. </p><p></p><p>It strikes me as unfortunate that the ABM web site lists performance specs for a loaded cartridge based on this bullet assuming a 26" barrel and sea level conditions, even though Bryan has established that the BC and downrange performance will be reduced under sea level conditions for a 1 in 10" twist.</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 983029, member: 28191"] Notes on Weapon Employment Zone Analysis of Berger 230 grain Tactical Match Hybrid in XM-2010 Rifle The analysis Bryan Litz published made two key assumptions in comparing the Berger 230 grain Tactical Match Hybrid with the 220 SMK load in his analysis. The fist assumption was that the 230 grain bullet could be pushed to 2900 fps in a 26" barrel and 2800 fps in the 24" barrel of the XM-2010. As it turns out the AMB published spec is 2850 fps in a 26" barrel which probably yields closer to 2750 fps in the 24" barrel of the XM-2010. The second assumption was that the 230 grain bullet would yield a G7 BC of 0.380 at sea level conditions in the 1 in 10" twist of the XM-2010 rifle. Since this was published in 2012 Bryan has revised his understanding of how stability impacts ballistic coefficient and his new stability calculator gives a G7BC of 0.361 at sea level conditions with a 1 in 10" twist. The calculator recommends a 9.25" twist for to achieve the full rated BC of this bullet. These factors will undoubtedly combine to reduce the gap between the 220 SMK and the 230 Target Match Hybrid in the WEZ analysis. One may further consider that our independent measurements of Berger ballistic coefficients has consistently yielded BCs 8% to 15% below Berger's published values. If the published BC of this bullet is also overly optimistic by 8% to 15%, the performance gap between the 220 SMK and the 230 Target Match Hybrid will be reduced even further. It strikes me as unfortunate that the ABM web site lists performance specs for a loaded cartridge based on this bullet assuming a 26" barrel and sea level conditions, even though Bryan has established that the BC and downrange performance will be reduced under sea level conditions for a 1 in 10" twist. [/QUOTE]
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Berger Bullets Announces Launch of a New Ammo Company
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