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Old 11th November 2014, 03:20 PM
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Brian.Samson Brian.Samson is offline
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Join Date: Jun 2009
Member of: Pontefract, Doncaster Airgun Range
Location: Doncaster
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Originally Posted by cloverleaf View Post
Interesting post.. for all my inquisitive nature I'd never considered the derivation of the constant. I've unquestioningly used 450240 ever since I first read it in Airgunner () at the age of about 15

Rob; as you point out this issue arises from varying available values for gravitational acceleration; would it not be easiest to work through the SI formula converting to imperial, using the standard gravitational acceleration constant of 9.80665m/s^2..?

As you rightly point out the potential for inaccuracy from such variations is pretty small - at this point I'd start worrying more about the accuracy of my measuring equipment, rounding errors etc
9.80665 = 32.174 which is what I tend to use.
That means you'd be using the constant 450436 in your calculations.

800 fps for an 8.4 pellet would be 11.935fpe
or 11.99fpe for an 8.44grn pellet.
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