Spring calculation

[steverebo]

I would like to work out what spring is in an Aeg I have just bought. Its an arp9 but has had a 200mm barrel fitted and 12:1 gears but no short stroking and shoots at around 305fps with .25 bb's

[BigStew]

Airsoft springs aren't made to high enough standard to work out and even if they were you got far too many variables that determine FPS that would have to be eliminated to make a calculation.

[Impulse]

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

[steverebo]

If only my arp9 had a quick change system lol

 

I was hoping maybe I could work out roughly what it was and but the next 1 or 2 up.

 

Never mind I guess I will hold off touching it till the wife goes away in a few weeks and then spend a day on it

[Impulse]

25 minutes ago, steverebo said:

If only my arp9 had a quick change system lol

 

I was hoping maybe I could work out roughly what it was and but the next 1 or 2 up.

 

Never mind I guess I will hold off touching it till the wife goes away in a few weeks and then spend a day on it

 

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

 

[Lozart]

3 hours ago, steverebo said:

I would like to work out what spring is in an Aeg I have just bought. Its an arp9 but has had a 200mm barrel fitted and 12:1 gears but no short stroking and shoots at around 305fps with .25 bb's

 

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]

8 hours ago, Lozart said:

 

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!

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]

9 hours ago, steverebo said:

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

 

Gotcha!

[SSPKali]

On 01/02/2023 at 00:24, steverebo said:

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

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