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Rifles, Reloading, Optics, Equipment
Reloading
Disappointing 308 MV.......and......which powder in Lapua factory 308?
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<blockquote data-quote="Brown Dog" data-source="post: 66152" data-attributes="member: 1622"><p>308sako and JDJones -Both, </p><p>Thanks.</p><p></p><p>I'm going to make myself sound stupid here:</p><p></p><p>My MV of 2580 was calculated (not chrono'd) based on field observation (ie actual comeups) and fitting those observations to my ballistics program.</p><p></p><p>Using the viht data for a 45gr charge of V140 (2670fps) and Nosler's stated BC (0.475 for the 165 NBT) as a start point, I 'massaged' the BC and/or the MV in the program until I got a match for my field observations.</p><p></p><p>Massaging the BC would not produce a fit. However, dropping the 'assumed' MV to 2580fps gave a perfect fit. I therefore took it that my MV was only 2580fps.</p><p></p><p>Due to the frustration indicated in my first post on this, I borrowed a chrono. </p><p>Today I clocked my rounds. They're doing 2740fps 10ft from the muzzle.</p><p></p><p>I'm pleased they're going faster than I thought, but can't understand why I'm having to do a 160fps MV 'fudge' in order to ballistically model the trajectory. (The program is based on the Pejsa model and validates when compared to data from other programs or –even- the Federal ammo catalogue data.)</p><p></p><p>I'm confused. Any ideas whats going on here?</p></blockquote><p></p>
[QUOTE="Brown Dog, post: 66152, member: 1622"] 308sako and JDJones -Both, Thanks. I’m going to make myself sound stupid here: My MV of 2580 was calculated (not chrono’d) based on field observation (ie actual comeups) and fitting those observations to my ballistics program. Using the viht data for a 45gr charge of V140 (2670fps) and Nosler’s stated BC (0.475 for the 165 NBT) as a start point, I ‘massaged’ the BC and/or the MV in the program until I got a match for my field observations. Massaging the BC would not produce a fit. However, dropping the ‘assumed’ MV to 2580fps gave a perfect fit. I therefore took it that my MV was only 2580fps. Due to the frustration indicated in my first post on this, I borrowed a chrono. Today I clocked my rounds. They’re doing 2740fps 10ft from the muzzle. I’m pleased they’re going faster than I thought, but can’t understand why I’m having to do a 160fps MV ‘fudge’ in order to ballistically model the trajectory. (The program is based on the Pejsa model and validates when compared to data from other programs or –even- the Federal ammo catalogue data.) I’m confused. Any ideas whats going on here? [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Disappointing 308 MV.......and......which powder in Lapua factory 308?
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