SR25 FPS Issue

[Mack]

I'm having some FPS issues with my CA SR25 shooting low. I've been working with Gman at AC on this so far. However we're kind of at a  point with this.

Here's what I have in it now...
CA Helical Gears
CA Bore Up Kit ( compression is good )
G&G Extended Piston
CA Hop Up Unit
G&G Bucking
Stock nub
Madbull 6.03 TBB
Systema PSG1 200% Spring
MOSFET

It is shooting a consistent 400 fps w/ .20's with all of this. My target is a 2 joule DM platform. The 200% spring, according to different sites, should put it close to that.

I've tried using the following parts in different combinations Madbull hop up, Madbull blue bucking, M130 spring, Duracon piston head, new OEM air nozzle, original OEM cylinder, piston, piston head, air nozzle and cylinder head. The different combos of these parts have yielded between 330 - 365 fps.

Any thoughts on what else can be done to hit that target other than upping the spring higher?

[SteevoLS]

Is there a good seal between the air nozzle, BB, and the hopup chamber?

[Mack]

Yup. That's one of the reasons why I we went back to the CA hop up.

[IronChef]

are u using the sr-25 specific gearsets??? dumb question, but i am a sr owner and mine shoots right at 400 with mild tweaks..getting one over 400 should be easy.

[Mack]

Yup. Bore-up kit, helicals and piston are all for the CA SR25.

There are no dumb questions especially with this. I'm sure it's going to be one of those duh answers. I've replaced just about all the internals so far or gone back to the originals. I think the only parts that haven't been touched are the tappet plate, trigger and anti reversal latch.

[Gman Chris]

I've been thinking about our next step with your SR25. I think that we need to kill the bore-up kit. See what it does without that. I've noticed that bore-ups tend to have compression issues.

[IronChef]

i dont have the bore up...

[Mack]

As long as I don't end up being on call this weekend, I'm hoping to take it to Trigger Time this weekend. Kinda do a stress test on it. Since it's still shooting at 400 fps I can run it full auto through a couple mags.

Then maybe magical airsoft fairy will come sprinkle pixie dust on it during the night and botta bing it'll be perfectly where I want it. 

[82dcustomer]

It could be the barrel too.  I have had two guns now that lost a lot fo fps just because of the barrel.  We have changed the hop up from one barrel to another and it fixed it.  Try swapping barrels out.

[Dominum]

^Ditto. Also look for hairline fractures on the piston head, cylinder head, air nozzle, and hopup chambers. Sometimes they are invisible unless you gently "bend" them. Also, even though that is the correct gearset, it is possible that the last tooth or teeth on the sector gear may have broken off, so it is not easily recognizable from ther normal angle. This would mean that the GB would function fine (as long as the broken tooth/teeth didn't fall in the wrong spot) but would only pull the piston back most of the way, causing a noticeable loss of FPS. Visually inspect both the sector gear and piston teeth closely, and make sure there are a total of 19 on both.

[Gman Chris]

^Ditto. Also look for hairline fractures on the piston head, cylinder head, air nozzle, and hopup chambers. Sometimes they are invisible unless you gently "bend" them. Also, even though that is the correct gearset, it is possible that the last tooth or teeth on the sector gear may have broken off, so it is not easily recognizable from ther normal angle. This would mean that the GB would function fine (as long as the broken tooth/teeth didn't fall in the wrong spot) but would only pull the piston back most of the way, causing a noticeable loss of FPS. Visually inspect both the sector gear and piston teeth closely, and make sure there are a total of 19 on both.

Henry: I've already done all of that.

Mike: Mack has a new barrel on the way. We'll swap it out when it shows up.

I think that the gearbox fairy needs to sprinkle some dust on it. 

[Dominum]

Wow, if it's none of those issues, no wonder you're in a qaundry! I can't think of what else it could be, I think you will need a fairy for this one.