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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Altitude vs. Barometric pressure
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<blockquote data-quote="triggerfifty" data-source="post: 115331" data-attributes="member: 4907"><p><strong>29.53 vs 29.92 In. Hg.</strong></p><p></p><p>Hi,</p><p></p><p>I've been developing data tables for years for SOE (which is my own company) and I did it on active duty for .50 cal rifles when I used them. The difference between these two is that the 29.53 In. Hg. is issued as a ballistic standard and agreement by Aberdeen Proving Grounds Ballistic Research Lab (BRL) a few decades back. It was done to standardize (but not a NATO standard) certain values of measurement to be used in the science of external ballistics. APG BRL Standards for air conditions are:</p><p></p><p>59 deg. F air temp</p><p>29.53 In. Hg. or 1000 mb air pressure</p><p>70 degrees ammunition temperature</p><p>78% humidity (which is a non-factor in LOW trajectory fire</p><p>0 degrees slant angle gun to target</p><p></p><p>The standard of 29.92 is an FAA and aviation standard. One of my trainers is a former pilot and says the same as the poster above saying that air pressure values are dialed into the altimeter so that the wheels are on the ground when landing or taking off, the altimeter reads 0. </p><p></p><p>Someone above also said, correctly, altitude means nothing, only the measured Raw air pressure is valuable. True. I helped develop the CheyTac Advanced Ballistic Computer that uses Doppler radar measurements to measure downrange speeds, drift, yaw, pitch, stability and launch velocities. That was 2 years of research. I wrote and modified the formulas that were used to write that software. It is in use by several military units in the US and overseas. It's been in use in combat since Jan 2002.</p><p></p><p>Very interesting subject.</p><p></p><p> <a href="http://www.snipingoperationsexecutive.org" target="_blank">Sniping Operations Executive</a></p></blockquote><p></p>
[QUOTE="triggerfifty, post: 115331, member: 4907"] [b]29.53 vs 29.92 In. Hg.[/b] Hi, I've been developing data tables for years for SOE (which is my own company) and I did it on active duty for .50 cal rifles when I used them. The difference between these two is that the 29.53 In. Hg. is issued as a ballistic standard and agreement by Aberdeen Proving Grounds Ballistic Research Lab (BRL) a few decades back. It was done to standardize (but not a NATO standard) certain values of measurement to be used in the science of external ballistics. APG BRL Standards for air conditions are: 59 deg. F air temp 29.53 In. Hg. or 1000 mb air pressure 70 degrees ammunition temperature 78% humidity (which is a non-factor in LOW trajectory fire 0 degrees slant angle gun to target The standard of 29.92 is an FAA and aviation standard. One of my trainers is a former pilot and says the same as the poster above saying that air pressure values are dialed into the altimeter so that the wheels are on the ground when landing or taking off, the altimeter reads 0. Someone above also said, correctly, altitude means nothing, only the measured Raw air pressure is valuable. True. I helped develop the CheyTac Advanced Ballistic Computer that uses Doppler radar measurements to measure downrange speeds, drift, yaw, pitch, stability and launch velocities. That was 2 years of research. I wrote and modified the formulas that were used to write that software. It is in use by several military units in the US and overseas. It's been in use in combat since Jan 2002. Very interesting subject. [url="http://www.snipingoperationsexecutive.org"]Sniping Operations Executive[/url] [/QUOTE]
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Altitude vs. Barometric pressure
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