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Old 28th May 2014, 09:26 PM
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Brian.Samson Brian.Samson is offline
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Member of: Pontefract, Doncaster Airgun Range
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Originally Posted by Ceathreamhnan View Post
Like I say, on a field (actually a dispersal area on a WWII airfield) on a flat farm.

I'm shooting at a card with a grid drawn on it parallel to the ground with a mildot ret lined up with the grid

I agree with your assertion that the extra distance wouldn't make any odds, much like the sin theta/theta = 1 thing for small angles. But I suspect, like you say, for diabolo pellets BC theory needs an extra complication.
I originally did the test to see for myself whether the suggested idea of rifling going in one direction would make a difference in POI for left v right wind, which I couldn't see. But both groups for left and right, with varying amounts of wind (it was very windy, around 2 mildots @10x at 45y), resulted in a lower average POI than you would get for the same setup with no wind.
It's a quandary that's for sure.. I wasn't really asking questions that needed to be answered, just coming up with things that people don't always consider when they do tests like this.

So for example - a flat field doesn't necessarily rule out a vertical component to the wind, a grid parallel to the ground doesn't rule out that the ground isn't level. If you're moving the target N,E,S,W - is there a chance that when you move it to a different direction it's 44 yards and when it goes to another it's 46 etc. again, not questions that I'm firing at you, just pointing out the dangers of drawing conclusions from tests that aren't controlled.

Look at it like this - if you got everything perfect and it was a fully controlled test - what possible reason is there to explain the result? If it's not the extra distance (I'm pretty sure it can't be that, because that can be calculated and it's very small) then what is it?

The only explanation I can think of is that something's amiss with the testing environment? Another possibility is precession due to barrel/twist rate and rifling marks perhaps??

What we need is a University to get a grant to study airgun pellet ballistics - if they can get grants to study the sogginess of cornflakes I'm sure they can get a grant to study something useful
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