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Extreme Long Range Hunting & Shooting (ELR)
Wind reading for +1K shots
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<blockquote data-quote="Topshot" data-source="post: 681435" data-attributes="member: 13285"><p><span style="font-family: 'Arial'"><span style="font-size: 10px">Boss Hoss,</span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">I make no derogatory statements about Mr Speedy Gonzalez ability as a shooter or his record in competition. He is obviously a well known a and respected shooter. However his statement on the effect of humidity is in error. Simple as that.</span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">This may be a typo or a misunderstanding of the facts, I don't know. He states that a 20% change in humidity will result in a 1 MOA change in point of impact. This is a vague statement as he does not define a distance that this 1 MOA change is made. </span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">In no way will a 20% change in humidity result in a 1 MOA change in POI at 100 yards or any distance under 1000 yards. In actual fact, the only change that I can find at 1000 yards is a mere 0.1 MOA. and that is in the opposite direction to what he states it will be.</span></span></p><p><span style="font-family: 'Arial'"><span style="font-size: 10px"> </span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">The effect of atmospheric conditions on a bullets trajectory is due to changes in air pressure, temperature and humidity. Variations in these three things, result in a change in air density and the speed of sound.</span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">While changes to air density have a large effect bullet drop, changes in the speed of sound have only a very minor effect on trajectory and mainly at extreme long range where the transonic barrier is encountered.</span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">A change of humidity from 0% to 100% at 59 degrees F, has only a 0.2% change in the speed of sound. So only a minor effect at best.</span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">Please read the effect on air density due to changes in humidity below and in the link provided, it helps describe why the effect on trajectory is opposite to what Mr Speedy states.</span></span></p><p> </p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">The effect on air density can be read here..... <a href="http://en.wikipedia.org/wiki/Density_of_air" target="_blank">Density of air - Wikipedia, the free encyclopedia</a> </span></span></p><p><span style="font-family: 'Arial'"><span style="font-size: 10px">But in short........ </span></span>The addition of <a href="http://en.wikipedia.org/wiki/Water_vapor" target="_blank">water vapor</a> to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive.</p><p>This occurs because the molecular mass of water (18 g/mol) is less than the molecular mass of dry air (around 29 g/mol). For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume (see <a href="http://en.wikipedia.org/wiki/Avogadro's_Law" target="_blank">Avogadro's Law</a>). So when water molecules (vapor) are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure or temperature from increasing. Hence the mass per unit volume of the gas (its density) decreases.</p><p> </p><p>A lot of the other tips that Mr Speedy gives sound like good advice. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p></blockquote><p></p>
[QUOTE="Topshot, post: 681435, member: 13285"] [FONT=Arial][SIZE=2]Boss Hoss,[/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]I make no derogatory statements about Mr Speedy Gonzalez ability as a shooter or his record in competition. He is obviously a well known a and respected shooter. However his statement on the effect of humidity is in error. Simple as that.[/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]This may be a typo or a misunderstanding of the facts, I don't know. He states that a 20% change in humidity will result in a 1 MOA change in point of impact. This is a vague statement as he does not define a distance that this 1 MOA change is made. [/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]In no way will a 20% change in humidity result in a 1 MOA change in POI at 100 yards or any distance under 1000 yards. In actual fact, the only change that I can find at 1000 yards is a mere 0.1 MOA. and that is in the opposite direction to what he states it will be.[/SIZE][/FONT] [FONT=Arial][SIZE=2] [/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]The effect of atmospheric conditions on a bullets trajectory is due to changes in air pressure, temperature and humidity. Variations in these three things, result in a change in air density and the speed of sound.[/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]While changes to air density have a large effect bullet drop, changes in the speed of sound have only a very minor effect on trajectory and mainly at extreme long range where the transonic barrier is encountered.[/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]A change of humidity from 0% to 100% at 59 degrees F, has only a 0.2% change in the speed of sound. So only a minor effect at best.[/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]Please read the effect on air density due to changes in humidity below and in the link provided, it helps describe why the effect on trajectory is opposite to what Mr Speedy states.[/SIZE][/FONT] [FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]The effect on air density can be read here..... [url=http://en.wikipedia.org/wiki/Density_of_air]Density of air - Wikipedia, the free encyclopedia[/url] [/SIZE][/FONT][FONT=Arial][SIZE=2][/SIZE][/FONT] [FONT=Arial][SIZE=2]But in short........ [/SIZE][/FONT]The addition of [URL="http://en.wikipedia.org/wiki/Water_vapor"]water vapor[/URL] to air (making the air humid) reduces the density of the air, which may at first appear counter-intuitive. This occurs because the molecular mass of water (18 g/mol) is less than the molecular mass of dry air (around 29 g/mol). For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume (see [URL="http://en.wikipedia.org/wiki/Avogadro's_Law"]Avogadro's Law[/URL]). So when water molecules (vapor) are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure or temperature from increasing. Hence the mass per unit volume of the gas (its density) decreases. A lot of the other tips that Mr Speedy gives sound like good advice. :) [FONT=Arial][SIZE=2][/SIZE][/FONT] [/QUOTE]
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