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Old 3rd October 2013, 10:44 AM
neilL neilL is offline
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Originally Posted by Brian.Samson View Post
Yup, all the rest looks ok, apart from the quoted line - that's not correct. Very odd I know, but the wind drift doesn't depend on side profile (according to ballistic theory). Unless that side profile has an effect on total time to target - i.e. the different profile causes more drag.

It took me a while to get my head around this when I started flying microlight aircraft, but it's the same thing.

When you're plotting the wind drift vector for an aircraft, how aerodynamic the aircraft is from it's side profile makes no difference whatsoever to the wind drift.

The reason is - the wind applies no sideways force to the aircraft, because the aircraft once airborne is a part of the atmosphere - so it's moving forwards through a substance (the air) that just happens to be moving sideways.

Well that's how it's been explained to me, any documents you read about wind drift for projectiles will tell you exactly the same thing and the calculation used in things like Chairgun (which just use a standard wind drift calculation) take no account of the side profile of a pellet.

It doesn't 'feel' right to me, but that's the accepted theory and has been for hundreds of years.
Hmm Yes. Perhaps easier to think of if you imagine water rather than air for some reason e.g. fast flowing river.

So the difference between a heavy and light pellet has to be just the actual BC. A higher BC equals shorter flight time and higher target velocity therefore less drift? So initial speed and BC are what matter for outdoor shooting?

BCs given are very small for pellets (0.021 for Exact) and any variation will have a much bigger impact.

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