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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
anyone have problems with jbm?
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<blockquote data-quote="Sam Aspacher" data-source="post: 856868" data-attributes="member: 53110"><p>Its my understanding that if you select the box std. atmosphere at altitude the program will ignore your inputs for temperature and air pressure and use the standard values for the given altitude you entered. If you want to enter a different value deselect that box. Also, be sure to consider the the "pressure is corrected" box. It will throw your numbers off if you're using a absolute pressure with that box checked.</p><p> </p><p>As for the Bcs, I'm not really sure. Anytime I've used the program I have just scrolled down and selected the bullet from the drop down list. Maybe thats what you did as well and thats why it ignored the values you manually entered again??</p><p> </p><p>Far as your energy comparison goes. I'd expect a 260ai with 140s to have more energy at that range then just about anything a 308 could shoot. Think your velocity is a little high for a 208 gr. My 308 shoots 168s at 2750. Seems like 40 grains heavier bullet along with reduced case capacity for a given coal would make that velocity unattainable. I very well could be wrong. If I am then that bullet at that speed might produce more energy at that range. It does have a higher bc after all. I'd start by verifying all the values and seeing what you get for a better comparision.</p><p> </p><p>Hope this helps you -Sam</p></blockquote><p></p>
[QUOTE="Sam Aspacher, post: 856868, member: 53110"] Its my understanding that if you select the box std. atmosphere at altitude the program will ignore your inputs for temperature and air pressure and use the standard values for the given altitude you entered. If you want to enter a different value deselect that box. Also, be sure to consider the the "pressure is corrected" box. It will throw your numbers off if you're using a absolute pressure with that box checked. As for the Bcs, I'm not really sure. Anytime I've used the program I have just scrolled down and selected the bullet from the drop down list. Maybe thats what you did as well and thats why it ignored the values you manually entered again?? Far as your energy comparison goes. I'd expect a 260ai with 140s to have more energy at that range then just about anything a 308 could shoot. Think your velocity is a little high for a 208 gr. My 308 shoots 168s at 2750. Seems like 40 grains heavier bullet along with reduced case capacity for a given coal would make that velocity unattainable. I very well could be wrong. If I am then that bullet at that speed might produce more energy at that range. It does have a higher bc after all. I'd start by verifying all the values and seeing what you get for a better comparision. Hope this helps you -Sam [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
anyone have problems with jbm?
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