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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
MOA vs. Bullet Drop Compensator
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<blockquote data-quote="Buffalobob" data-source="post: 143668" data-attributes="member: 8"><p>You can easily run several different altitudes and tempratures for you bullet with a ballistics program and come up with the compensation needed for your BDC.</p><p></p><p>Example is that my elk rifle changes about 0.1 inches of drop for every ten degrees fahrenhiet at 1000 yards. Put differently, every ten degrees of temperature causes the gun to shoot one inch high or lower at 1000 yards. In other words for me to miss based upon temperature it would need to be hot enough to fry and egg on a rock or so cold I would have quit and gone home. I believe I would notice that.</p><p></p><p>In as far as altitude goes, every thousand feet of altitude changes my drop by 0.2 inches. This is two inches low or high at 1000 yards. A 3000 feet change is necessary in order for me to miss a deer and about 5000 feet change to miss an elk. If I happen to know these numbers for correcting altitude and temperature in advance I can simply take my BDC knob and back it up or down by the amount needed at the ratio of the distance and still make a clean hit every time.</p><p></p><p>One of the great lucky thing for us elk hunters is the adiabatic lapse rate. This causes it to get colder the higher you go in altitude which partially (but not wholly)offsets in opposite directions the errors for a BDC (5.5 degrees F per 1000 feet altitude). How very nice. /ubbthreads/images/graemlins/grin.gif Of course you want to pitch your camp down low where it is warm and hunt high where it is cold. /ubbthreads/images/graemlins/grin.gif</p><p>However if you change bullets you will be in for major grief with a BDC. That will be way too much math to be calculating before every shot, even if you are good at math.</p><p></p><p></p><p>All of that said, it is simpler to just have straight turrets and the correct drop chart for the day taped to your stock or in your shirt pocket.</p></blockquote><p></p>
[QUOTE="Buffalobob, post: 143668, member: 8"] You can easily run several different altitudes and tempratures for you bullet with a ballistics program and come up with the compensation needed for your BDC. Example is that my elk rifle changes about 0.1 inches of drop for every ten degrees fahrenhiet at 1000 yards. Put differently, every ten degrees of temperature causes the gun to shoot one inch high or lower at 1000 yards. In other words for me to miss based upon temperature it would need to be hot enough to fry and egg on a rock or so cold I would have quit and gone home. I believe I would notice that. In as far as altitude goes, every thousand feet of altitude changes my drop by 0.2 inches. This is two inches low or high at 1000 yards. A 3000 feet change is necessary in order for me to miss a deer and about 5000 feet change to miss an elk. If I happen to know these numbers for correcting altitude and temperature in advance I can simply take my BDC knob and back it up or down by the amount needed at the ratio of the distance and still make a clean hit every time. One of the great lucky thing for us elk hunters is the adiabatic lapse rate. This causes it to get colder the higher you go in altitude which partially (but not wholly)offsets in opposite directions the errors for a BDC (5.5 degrees F per 1000 feet altitude). How very nice. [img]/ubbthreads/images/graemlins/grin.gif[/img] Of course you want to pitch your camp down low where it is warm and hunt high where it is cold. [img]/ubbthreads/images/graemlins/grin.gif[/img] However if you change bullets you will be in for major grief with a BDC. That will be way too much math to be calculating before every shot, even if you are good at math. All of that said, it is simpler to just have straight turrets and the correct drop chart for the day taped to your stock or in your shirt pocket. [/QUOTE]
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MOA vs. Bullet Drop Compensator
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