I've just recived a message form D_Hall, he didn't give a direct answer but he provided a link ---> http://en.wikipedia.org/wiki/Drag_coefficient# now I feel like an idiot... well not exactly like a complete idiot but anyway an idiot...
I've seen that page but I was not sure whether it is correct... well check it on your own but the way I understand it it means that cd value (drag coef) of smooth sphere is 0.1 (0.4 for rough sphere.... ) now the question is -> how smooth does the sphere have to be to be regarded as a smooth sphere?
@jrrwd yeah of course I meant curving them in one direction otherwise it wouldn't make sense
Do a experiment, shoot at different psi's and see how far they fly straight at different pressures, if you can still see them that far out, lol.
lol I can see whether they fly straigh or not... but i don't usually see where they hit.. well to be more precise I see them when they hit the concrete wall surounding my property (it is located about 100 - 120m away from the place where I shoot and I am generaly trying to avoid hiting it becasue there is a road behind it ).. some of the marbles explode on hitting it...
anyway really try shooting marbles on a sunny day it really looks cool when you see them flying in random directions
@ant thx! but now I am confused why it isn't 0.1 or something close to 0.1 ?
D_hall also wrote that
(I hope he doesn't mind quoting his message but paraphrasing isn't something I do with pleasure)these things do not scale perfectly. A sphere of size X doesn't necessarily have the same Cd as a sphere of size Y. Will it be close? Yes. Identical? Not necessarily.
I suspect that the problem with scaling cd value, small imperfections on the surface of BBs as well as calculation errors might have affected your result (0.25)...(but still 0.25 sounds reasonable for me)
now what does it mean for spudding community ?
that we cannot tell for sure what's the exact cd value for a given spherical ammo without testing it first but we may assume that it is close to 0.25