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The Basics, Starting Out
Drag functions and drop charts
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<blockquote data-quote="Mysticplayer" data-source="post: 113427" data-attributes="member: 8947"><p>I have little doubt that Sierra uses the G1 function in their BC calcs and that the tests done back then was a fair representation of the bullets manf at that time.</p><p></p><p>However, times have changed and so have bullet profiles.</p><p></p><p>We now have bullets of same weight with a huge variety of shapes and lengths. We now have both secant and tangent ogives. Bullets made with a variety of shapes usually lumped as VLD bullets.</p><p></p><p>We have poly tips, grooved bullets, small HP, wide HP, trimmed HP and on it goes.</p><p></p><p>So G1 does not represent all bullets manf today. All one needs to do is shoot conventional HP bullets like Sierra Matchking next to HP like the Lapua Scenar or poly tips like the Amax, SST, interbond, ballistic tip/accubond.</p><p></p><p>Although the BC suggests their ballistics to be similar, drop at distance indicates otherwise.</p><p></p><p>When I did my own tests a few years ago, I compared Nosler J4 (identical to Sierra MK), Nosler BT and Hornady Amax of equal weight. All launched at the same velocity as it was measured during firing. All had basically the same 100yd zero.</p><p></p><p>At 700yds, the HP bullets dropped consistently more then the poly tipped bullets. Impact groups/accuracy was similar between bullets. The drop extended as distance increased to 2 to 3MOA more scope elevation needed for the HP bullets at 900yds.</p><p></p><p>Recent tests with SST and Interbonds show that these can fly even flatter. Bullet lengths have increased for the given weight. This indicates an increase in streamlined shape. However, printed BC is pretty close to the same.</p><p></p><p>While playing with Amax in a few rifles at distances out to 940yds, the drop charts used would not agree with real world impacts. The real world drops were substantially less.</p><p></p><p>By playing with the program, nothing worked. Wasn't until I started plugging in different G functions that things started to agree.</p><p></p><p>So, G1 may work for some bullets very well, they don't work for all bullets today. By the way, the amax was a 162gr 7mm and the data agreed with my shooting when I used a G7 drag function with the printed BC of 0.625.</p><p></p><p>Now compare that to the G1 value....</p><p></p><p>Jerry</p></blockquote><p></p>
[QUOTE="Mysticplayer, post: 113427, member: 8947"] I have little doubt that Sierra uses the G1 function in their BC calcs and that the tests done back then was a fair representation of the bullets manf at that time. However, times have changed and so have bullet profiles. We now have bullets of same weight with a huge variety of shapes and lengths. We now have both secant and tangent ogives. Bullets made with a variety of shapes usually lumped as VLD bullets. We have poly tips, grooved bullets, small HP, wide HP, trimmed HP and on it goes. So G1 does not represent all bullets manf today. All one needs to do is shoot conventional HP bullets like Sierra Matchking next to HP like the Lapua Scenar or poly tips like the Amax, SST, interbond, ballistic tip/accubond. Although the BC suggests their ballistics to be similar, drop at distance indicates otherwise. When I did my own tests a few years ago, I compared Nosler J4 (identical to Sierra MK), Nosler BT and Hornady Amax of equal weight. All launched at the same velocity as it was measured during firing. All had basically the same 100yd zero. At 700yds, the HP bullets dropped consistently more then the poly tipped bullets. Impact groups/accuracy was similar between bullets. The drop extended as distance increased to 2 to 3MOA more scope elevation needed for the HP bullets at 900yds. Recent tests with SST and Interbonds show that these can fly even flatter. Bullet lengths have increased for the given weight. This indicates an increase in streamlined shape. However, printed BC is pretty close to the same. While playing with Amax in a few rifles at distances out to 940yds, the drop charts used would not agree with real world impacts. The real world drops were substantially less. By playing with the program, nothing worked. Wasn't until I started plugging in different G functions that things started to agree. So, G1 may work for some bullets very well, they don't work for all bullets today. By the way, the amax was a 162gr 7mm and the data agreed with my shooting when I used a G7 drag function with the printed BC of 0.625. Now compare that to the G1 value.... Jerry [/QUOTE]
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