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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Altitude vs. Barometric pressure
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<blockquote data-quote="Eaglet" data-source="post: 85247" data-attributes="member: 3756"><p>Perry also says this:</p><p></p><p> [ QUOTE ]</p><p>A distinctive feature offered by Exbal is the ability to capture and remember sight in conditions. Lets suppose that you establish a great load for your brand new 300 Win Short Magnum with a 180 gr bullet chronographed at 3070 feet per second. Lets say you live in Corpus Christi, Texas which is 50 feet above sea level. Further lets assume you that you sight in your rifle during June when the temperature in early morning (when the wind is minimal) will be about 80 degrees Farenheit. Not only that, but you have established a sight in such that your bullet path is never above three inches high, or below three inches low all the way out to 275 yards. This concept is called point blank range. In this case you could aim at the middle of a six inch target and always strike it if it is within 275 yards. </p><p></p><p>Preparation: Lets assume you have put a lot of effort into establishing this load and practicing, and have used up two hundred rounds of ammo (and precious barrel life). Now you get the good news that you drew an Elk permit in Wyoming. You will be hunting at 10000 feet elevation and the temperature is typically 30 degrees in late October. Without a ballistic calculator you will have no choice but to try and sight in again when you get to Wyoming. This may not work out too well because you will probably not have a bench rest to shoot from and you will surely make a lot of noise doing it. Trying to sight in across the hood of a pickup truck leaves a lot to be desired. </p><p></p><p>Exbal offers an alternative to that scenario. If you have Exbal "remember the sight in conditions" you can establish field conditions (altitude, temperature, etc) that match the ones you anticipate in Wyoming. Then Exbal will determine the bullet path that will occur in Wyoming, even though you sighed in at sea level. You can use the Excel interface to create a reference card and print it out and laminate it to carry with you. Now you can take full advantage of all the effort you put into creating your ideal load and you will know exactly how it will perform on your hunting trip. Having one less thing to worry about is a good thing. Thus another reason for using Exbal is that it enables you to get ready in advance.</p><p></p><p>[/ QUOTE ]</p><p></p><p>Therefore it's important that when using Exbal you input the elevation you zero-in for including barometric pressure, temp. and humidity... you save this info. and when you move to different elevations you input your new information including elevation and Exbal will give you the right info. If you make the Elevation zero then you're defeating the purpose.</p><p>Remember, for barometric pressure you want to enter is not the corrected pressure... the absolute pressure. If you do not have that info. then check the box next to it and Exbal will calculate the Standard Pressure for that given Elevation... that's another reason you need to input the elevation you're shooting at.</p><p></p><p>I really know how to use the Explorer Ballistic Program, and to 1000 yards it gives exactly the same values with Exbal. I played with both programs and using different elevations and they both agree. In <strong>Ballistic Explorer</strong> you enter the sea level corrected Barometric pressure for what ever elevation you're shooting at, you also enter the Elevation you're shooting at and when you change Elevations the barometric pressure is changed for you automatically; this takes place inside the program to my understanding.</p><p>I hope all this helps... We just have to learn how each individual program works, how the programmer intended it to work. </p><p></p><p>Javier O Moncada.</p></blockquote><p></p>
[QUOTE="Eaglet, post: 85247, member: 3756"] Perry also says this: [ QUOTE ] A distinctive feature offered by Exbal is the ability to capture and remember sight in conditions. Lets suppose that you establish a great load for your brand new 300 Win Short Magnum with a 180 gr bullet chronographed at 3070 feet per second. Lets say you live in Corpus Christi, Texas which is 50 feet above sea level. Further lets assume you that you sight in your rifle during June when the temperature in early morning (when the wind is minimal) will be about 80 degrees Farenheit. Not only that, but you have established a sight in such that your bullet path is never above three inches high, or below three inches low all the way out to 275 yards. This concept is called point blank range. In this case you could aim at the middle of a six inch target and always strike it if it is within 275 yards. Preparation: Lets assume you have put a lot of effort into establishing this load and practicing, and have used up two hundred rounds of ammo (and precious barrel life). Now you get the good news that you drew an Elk permit in Wyoming. You will be hunting at 10000 feet elevation and the temperature is typically 30 degrees in late October. Without a ballistic calculator you will have no choice but to try and sight in again when you get to Wyoming. This may not work out too well because you will probably not have a bench rest to shoot from and you will surely make a lot of noise doing it. Trying to sight in across the hood of a pickup truck leaves a lot to be desired. Exbal offers an alternative to that scenario. If you have Exbal “remember the sight in conditions” you can establish field conditions (altitude, temperature, etc) that match the ones you anticipate in Wyoming. Then Exbal will determine the bullet path that will occur in Wyoming, even though you sighed in at sea level. You can use the Excel interface to create a reference card and print it out and laminate it to carry with you. Now you can take full advantage of all the effort you put into creating your ideal load and you will know exactly how it will perform on your hunting trip. Having one less thing to worry about is a good thing. Thus another reason for using Exbal is that it enables you to get ready in advance. [/ QUOTE ] Therefore it's important that when using Exbal you input the elevation you zero-in for including barometric pressure, temp. and humidity... you save this info. and when you move to different elevations you input your new information including elevation and Exbal will give you the right info. If you make the Elevation zero then you're defeating the purpose. Remember, for barometric pressure you want to enter is not the corrected pressure... the absolute pressure. If you do not have that info. then check the box next to it and Exbal will calculate the Standard Pressure for that given Elevation... that's another reason you need to input the elevation you're shooting at. I really know how to use the Explorer Ballistic Program, and to 1000 yards it gives exactly the same values with Exbal. I played with both programs and using different elevations and they both agree. In [b]Ballistic Explorer[/b] you enter the sea level corrected Barometric pressure for what ever elevation you're shooting at, you also enter the Elevation you're shooting at and when you change Elevations the barometric pressure is changed for you automatically; this takes place inside the program to my understanding. I hope all this helps... We just have to learn how each individual program works, how the programmer intended it to work. Javier O Moncada. [/QUOTE]
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