Spring calculation
- Thread starter steverebo
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Impulse
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- Apr 18, 2019
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Let me throw a fun little tidbit into this...
GPA m120 spring in my SR-25 - 0.6J
ZCI m120 spring in my SR-25 - 1.1J
(I think this has something to do with the ZCIs being a bit more snug around the spring guide as there's also less twangy noises with them too. Also, lower power because the v2.5 gearbox is longer and therefore springs aren't under the same tension as in a regular v2 gearbox)
Also, when I did my first VSR build I bought a Laylax m150 for it as that was supposedly the 500fps one. Turns out it was around 2.9J in my build, and then the Rapax 2J spring was 2.5J
Basically, @BigStew has it correct; springs are a bit of a crapshoot, though they will be manufactured to "roughly this velocity on a .2". m100 should be roughly 100m/s (328fps) on a .2, m110 should be roughly 110m/s on a .2 etc etc, however there are so many different variables that go into the power like air seal, hop up, BB weight to name a few. Best way to approach springs is experimentation. Fortunately they're not an expensive part, but it's always worth buying a few different powers and seeing what works best in your build. I only have two AEGs and I own probably about 20 springs (though that's also because the SR-25 has a quick change spring system so I wanted a few powers for different DMR limits around the country, as well as a 1.1J one for no MED default
GPA m120 spring in my SR-25 - 0.6J
ZCI m120 spring in my SR-25 - 1.1J
(I think this has something to do with the ZCIs being a bit more snug around the spring guide as there's also less twangy noises with them too. Also, lower power because the v2.5 gearbox is longer and therefore springs aren't under the same tension as in a regular v2 gearbox)
Also, when I did my first VSR build I bought a Laylax m150 for it as that was supposedly the 500fps one. Turns out it was around 2.9J in my build, and then the Rapax 2J spring was 2.5J
Basically, @BigStew has it correct; springs are a bit of a crapshoot, though they will be manufactured to "roughly this velocity on a .2". m100 should be roughly 100m/s (328fps) on a .2, m110 should be roughly 110m/s on a .2 etc etc, however there are so many different variables that go into the power like air seal, hop up, BB weight to name a few. Best way to approach springs is experimentation. Fortunately they're not an expensive part, but it's always worth buying a few different powers and seeing what works best in your build. I only have two AEGs and I own probably about 20 springs (though that's also because the SR-25 has a quick change spring system so I wanted a few powers for different DMR limits around the country, as well as a 1.1J one for no MED default
Impulse
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- Apr 18, 2019
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Why change it? 305fps on a .25 is exactly where you want it, surely? Much more and it'll be over the limit of 1.14J
View attachment 101150
Lozart
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- Jun 24, 2013
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This is the one you want to use for CQB right? It's pretty much spot on 340FPS/1.08J. I'd leave it alone!
steverebo
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- Dec 16, 2021
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My local cqb site has a limit of 330 fps with .20 so 1j or 295fps with .25 so I need to come down a bit but will be short stroking 4 teeth as this is solely a semi auto build which is why I wanted to know roughly what spring I'm at so I can take the roughly 60 fps I lose from the short stroking and add that with a spring upgrade to bring me between 320 and 330 on .20
Lozart
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- Jun 24, 2013
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My ex-AKS74U was short stroked by 4 teeth and ran a GPA M120 spring (from the great AK2M4) and was around 320fps on a 0.20g
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