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Old November 3rd, 2008, 22:25   #17
Skladfin's Avatar
Join Date: Dec 2006
Location: Vancouver, B.C
Originally Posted by mcguyver View Post
Sorry, there is nothing incorrect in what I said.

Explain please why my M16A3 PTW will shoot 0.25g BB at 497 fps but will shoot a .20g at 530 fps? 20% decrease in BB mass but only a 6.6% increase in velocity? Don't worry, I already know the answer.

My old Marui G3 shot 265 with 0.25g and 295 with .20g. Same BBs (I haven't changed brands in years). Same 20% decrease in mass, but now an 11% increase in velocity.
that's a really dumb theory you have there, 20% decrease in mass doesn't mean 20% increase in velocity.

things don't work like that, it always have to follow a formula. We'll keep it simple, you can find the difference in velocity between 0.20g and 0.25g using 2 physics formulas

F= ma
vf(squared) = vi(squared) + 2ad

F = force applied
m = mass
a = acceleration
vf = Final velocity when leaving the barrel
vi = initial velocity before force being applied(so in this case, zero)
d = distance traveled between vi to vf

did some calculations and here are the results(In the calculation, I'm assuming that it fires 400FPS with 0.25g)
I also neglect any friction force between barrel and BB during barrel travel, and hop up effect.

From my chrono results(and yours too) shows that the difference in velocity between 0.20 and 0.25g IS roughly 40FPS give or take a few FPS (because of hop up/friction).

so no, 20% mass decrease in mass does NOT equal 20% increase in velocity.

Last edited by Skladfin; November 3rd, 2008 at 22:28..
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