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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Altitude vs. Barometric pressure
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<blockquote data-quote="Litehiker" data-source="post: 1011854" data-attributes="member: 54178"><p>Thanks Doc, </p><p>Your input was needed here, especially regarding the Kestrel 4500/AB model. Unless it is a military device there is no other device I know of that will sense and calculate for so many environmental parameters as that unit for rifle firing solutions. It even considers internal ballistics in the form of twist rate that must be entered into the K 4500/AB to calculate spin drift.</p><p></p><p>Also the fact that Kestrel has now added Applied Ballistics software gives me even more confidence in it. Brian Litz and company have actually tested the ballistics and not just extrapolated from ballistic theory. As the song says, "There's nothin' like the real thing Baby."</p><p></p><p>My understanding of altitude density is that is the TRUE factor that matters, not actual altitude,d because, as you mentioned above, it is the <em>atmospheric "density" </em>the bullet must pass through. A very hot day (say, 100 F.) at 6,000 ft. and a very cold day (say 0 F.) at the same altitude, given the same humidity, will produce very different atmospheric densities. Hot air is "thin" (less atmosphere) and cold air is dense. Of course relative humidity and air pressure differences caused by weather fronts is a variable the also unit takes into account.</p><p></p><p></p><p>The K 4500/AB unit's internal compass is used to calculate north/south <em>coriolis effect </em>and east/west effect (I forgot the term for this).</p><p></p><p> Now if there were a way to use laser light to calculate average wind over the distance-to-target we'd have an even better solution. As it is the wind at the shooter's position is the most important reading in terms of effects on bullet wind drift and by taking two readings, the full wind and the wind on the line of firing to target the unit calculates a proper <em>wind value</em>.</p><p></p><p>QUESTION: With all other factors being equal will, for example, a .30 cal., 200 gr. bullet fired from a .300 Win mag cartridge with a 1:10 twist barrel drift more than the same bullet fired from a 1:8 twist barrel? I'd guess the faster twist rate gives more gyroscopic stability and perhaps less spin drift.</p></blockquote><p></p>
[QUOTE="Litehiker, post: 1011854, member: 54178"] Thanks Doc, Your input was needed here, especially regarding the Kestrel 4500/AB model. Unless it is a military device there is no other device I know of that will sense and calculate for so many environmental parameters as that unit for rifle firing solutions. It even considers internal ballistics in the form of twist rate that must be entered into the K 4500/AB to calculate spin drift. Also the fact that Kestrel has now added Applied Ballistics software gives me even more confidence in it. Brian Litz and company have actually tested the ballistics and not just extrapolated from ballistic theory. As the song says, "There's nothin' like the real thing Baby." My understanding of altitude density is that is the TRUE factor that matters, not actual altitude,d because, as you mentioned above, it is the [I]atmospheric "density" [/I]the bullet must pass through. A very hot day (say, 100 F.) at 6,000 ft. and a very cold day (say 0 F.) at the same altitude, given the same humidity, will produce very different atmospheric densities. Hot air is "thin" (less atmosphere) and cold air is dense. Of course relative humidity and air pressure differences caused by weather fronts is a variable the also unit takes into account. The K 4500/AB unit's internal compass is used to calculate north/south [I]coriolis effect [/I]and east/west effect (I forgot the term for this). Now if there were a way to use laser light to calculate average wind over the distance-to-target we'd have an even better solution. As it is the wind at the shooter's position is the most important reading in terms of effects on bullet wind drift and by taking two readings, the full wind and the wind on the line of firing to target the unit calculates a proper [I]wind value[/I]. QUESTION: With all other factors being equal will, for example, a .30 cal., 200 gr. bullet fired from a .300 Win mag cartridge with a 1:10 twist barrel drift more than the same bullet fired from a 1:8 twist barrel? I'd guess the faster twist rate gives more gyroscopic stability and perhaps less spin drift. [/QUOTE]
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Altitude vs. Barometric pressure
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