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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Coriolis effect
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<blockquote data-quote="Brown Dog" data-source="post: 29328" data-attributes="member: 1622"><p>Following on from Dave's premise that there could be less interesting things to do...and besides, it's now dark in my part of the world.....</p><p></p><p>I just grabbed a few figures from an artillery firing table to try to quantify the sort of effects we're talking about. The proj in question has an mv of 820m/s and a BC of around 0.3 [which surprised me until I considered how much less dense HE is than lead].</p><p></p><p>Firing at latitude of 50 degrees North, with a target at a range of 2000m (chosen so that there might be some read across to rifle shooters):</p><p></p><p>Standard stuff:</p><p>Time of flight is 2.7 sec</p><p>Drift requires a 0.5mil left correction (ie 1 metre at this range).</p><p></p><p>Rotation of the Earth stuff:</p><p>On <strong>all</strong> bearings of fire a 0.1mil left correction is required (ie 20cm at this range).</p><p>Easterly fire requires an elevation reduction equivalent to the target being 13 metres closer.</p><p>Westerly fire requires an elevation increase equivalent to the target being 13 metres further away.</p><p>(in both cases this value gradually reduces to zero as the bearing moves to due N or S.)</p><p></p><p>Bet that's surprised a few people!</p><p></p><p>There are a bunch of factors resulting from the effects caused by the Earth's rotation -Coriolis is just one of them. They interact to sometimes cancel each other, sometimes add to each other -depends on lots of things [eg consider the difference between a shot fired from zero degrees to a target at 10 degrees North (not too big a difference between Earth surface speed at both locations) versus from 80 to 90 degrees North. Factor this against Projectile Lag (time of flight and max vertex height related) and don't forget that for Westerly fire the Earth 'rises' to meet the round whereas for Easterly it 'drops away' to let the round go long] </p><p></p><p>The artillery values given are therefore the overall result of the interaction of all the effects that can be grouped as being caused by the Earth's rotation. There's little point in considering Coriolis in isolation!</p><p></p><p>I hope that's thoroughly confused everyone!</p></blockquote><p></p>
[QUOTE="Brown Dog, post: 29328, member: 1622"] Following on from Dave's premise that there could be less interesting things to do...and besides, it's now dark in my part of the world..... I just grabbed a few figures from an artillery firing table to try to quantify the sort of effects we're talking about. The proj in question has an mv of 820m/s and a BC of around 0.3 [which surprised me until I considered how much less dense HE is than lead]. Firing at latitude of 50 degrees North, with a target at a range of 2000m (chosen so that there might be some read across to rifle shooters): Standard stuff: Time of flight is 2.7 sec Drift requires a 0.5mil left correction (ie 1 metre at this range). Rotation of the Earth stuff: On [B]all[/B] bearings of fire a 0.1mil left correction is required (ie 20cm at this range). Easterly fire requires an elevation reduction equivalent to the target being 13 metres closer. Westerly fire requires an elevation increase equivalent to the target being 13 metres further away. (in both cases this value gradually reduces to zero as the bearing moves to due N or S.) Bet that's surprised a few people! There are a bunch of factors resulting from the effects caused by the Earth's rotation -Coriolis is just one of them. They interact to sometimes cancel each other, sometimes add to each other -depends on lots of things [eg consider the difference between a shot fired from zero degrees to a target at 10 degrees North (not too big a difference between Earth surface speed at both locations) versus from 80 to 90 degrees North. Factor this against Projectile Lag (time of flight and max vertex height related) and don't forget that for Westerly fire the Earth 'rises' to meet the round whereas for Easterly it 'drops away' to let the round go long] The artillery values given are therefore the overall result of the interaction of all the effects that can be grouped as being caused by the Earth's rotation. There's little point in considering Coriolis in isolation! I hope that's thoroughly confused everyone! [/QUOTE]
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