Spring Chart

[gixser13]

http://www.airsoftcanada.com/SpringChart.html

[Ganef]

Good stuff, if only we could get more people solving these issues for other guns and other variants then we would have airsoft down to a science.

[Airsofter1]

This is a great resource!  Thanks Dave!

[Victor3]

I dunno....seems a little inaccurate to me. I have PDI 170%'s in all my guns and the most I have ever got out of them is 399....not even close to 420.65

[Harley]

What he failed to include in his data is altitude and air density.  Those two are big factors.  But as Victor3 stated, most PDI170's I've installed only averaged around 390 to 400fps.  On the rare occasion I have seen them go to 420, but that's very rare, and I would almost sumize that it was a mispackaged spring in those cases.

[Airsofter1]

He also puts PDI 150% springs at 395.45 avg.  All of the ones I have installed usually avg 360 fps.  But... (read whats next)

I have a PDI 170 spring that chrono'd out of my SAW last at an avg of 410-420.  But that was also with a full cylinder, and silent piston head.  Without those items installed it might have been closer to 400.  That guy was shooting his out of a tight bore barrel and a tapered cylinder which might have affected it some also, as well as the altitude and air density.

If you figure a 20 FPS variance between two of the same spring it doesn't seem so far off.  You always here about Systema M120 people install that shoot as low as 370 fps, but the next guys M120 is shooting 420 fps.

[Victor3]

Just for clarification all my guns are the same; PDI 170, full cyl. , Systema brass tightbores. And where we are (approx. 1000' ASL) they all shoot between 395 - 400 consistently. Air density definately makes a diff. they all shoot a bit less when we head up to Prescott (5260')