[Cochise]

Well, assuming the stock fps is 280 fps you can do the following.

280 * sqrt(spring%/100)

Thus, your 300% spring should shoot approximately 484 fps optimally.

For interest, this uses the conservation of energy law and the proportion of approximate kinetic energies represented by
.5 * mass1 * velocity1^2 * (spring% / 100) =
.5 * mass2 * velocity2^2
Since mass1 = mass2 and .5 = .5 and velocity1 = 280 fps
280fps^2 * (spring% / 100) = velocity2^2

Finally:
velocity2 = 280 * ((spring% / 100)^.5) fps

Hope this helps more than hurts.

Physics is Phun!

[Cochise]

It should be noted that Systema and KM springs are rated differently than % springs.  Systema type springs are marked as the meters per second with a .20 BB.

Thus, the conversion is easier.

Mark m / sec * 3.31 ft. / m = Mark * 3.31 fps

Thus, an M120 shoots 397 optimally.

Hope this helps more than hurts

[Cochise]

I use the term optimally, though I should use theoretically.

Gearboxes are not perfect machines and thus you will not get 100% of the springs energy in the BB.  Further, there is manufacturing variances.  As a study of variances, imagine 10 people all with brand new Classic Army AEGs of the same make and model.  More than likely, 3 will fire above 300 fps, 3 will fire just under 300 fps, 2 will fire stock fps, while the last two will not fire due to batteries either not being charged or forgorsoft Atlanta has 10 30 rnd mags for $40.00. (just thought I'd mention it cause I am thinking about getting some for realism sake.)

[Long Trang]

Im in a bit of a bind right now.  Ive got a m24 with a CA 300% spring and the bolt pull is almost impossible for me.  First is there a way to fix this like cutting coils etc?  

Now the main question, what is the normal FPS output of a 210% spring or a 190% spring?  Does anyone know those statistics?  if i cant fix the 300% spring pull then i need to swap the spring to a 210 or 190 but want to know what fps i would get.  thanks for the help.