CA SR25 FPS Issue

[Mack]

I'm doing some upgrades on my SR25 and the speed is consistantly low, 350 fps w/ M130. Since the gearbox is elongated the spring doesn't have the normal amount of tension while in the released position.

I've read one post that suggested upping the spring higher in order to get the desired fps. i.e. an M130 instead of an M120. Would possibly putting some kind of spacer inside of the piston or on the spring guide create the same effect as if it were a standard gearbox? Any other ideas?

I'm trying to build a 500+ fps AEG DM platform. I want to run the lightest spring I can to keep the stress down. I've already installed helicals, bore-up kit, reinforced piston, MOSFET, motor and hop-up unit. Shortly I'll be replacing my current TBB with a custom length one.

[Ash]

How is the compression with the air nozzle. I know that the extended V2 has an extra long air nozzle which can cause poor compression. Also what brand of bore up kit is it. I have had issues with CA bore kits, having not so good compression.

[Cap n pickles]

I'm doing some upgrades on my SR25 and the speed is consistantly low, 350 fps w/ M130. Since the gearbox is elongated the spring doesn't have the normal amount of tension while in the released position.

I've read one post that suggested upping the spring higher in order to get the desired fps. i.e. an M130 instead of an M120. Would possibly putting some kind of spacer inside of the piston or on the spring guide create the same effect as if it were a standard gearbox? Any other ideas?

I'm trying to build a 500+ fps AEG DM platform. I want to run the lightest spring I can to keep the stress down. I've already installed helicals, bore-up kit, reinforced piston, MOSFET, motor and hop-up unit. Shortly I'll be replacing my current TBB with a custom length one.

I think you may have problems coming up on that 500 FPS area anyways.

I would try throwing in other springs, 150, 170 maybe.

[GacktC]

M150 & 170 will cause so much stress to the mechbox tho..

[Mtgriz]

Try a PSG1 length spring like everyone else with an upgraded CA25.

My CA25 is at 550 FPS, PSG1 worked for me.

[Jewish Ninja]

Try a PSG1 length spring like everyone else with an upgraded CA25.

My CA25 is at 550 FPS, PSG1 worked for me.

This is what I'd suggest. I'm only getting around the same FPS (350) with a regular M120, so I'm gonna try going that route and seeing if it works better!

[Mack]

Thanks for the info guys. I didn't realize the PSG1 had a longer spring. Any idea if the fps is same as the PSG1 rating?

Ash - I do have the CA bore up kit. Compression is good. Had to replace the piston o-ring and replaced the air nozzle. Part of the lip that seats the nozzle was broke when I got it.

[Mack]

Alright so I added a PSG1 200% spring. That put the fps up to the 370 fps range. In troubleshooting, I pulled out the Madbull hop up and Blue bucking. I put the stock CA hop up and bucking back in. Now it's shooting a consistent 400fps w/.20's. That seems low considering the spring and other upgrades.

Before all of the upgrades it was shooting 298 - 325 fps with an M120 spring.

Any thoughts?

If this helps here is a list of relevant parts by brand installed now...

CA Hop Up
CA Bucking
Standard nub
CA Bore Up ( compression is good )
Madbull 509mm 6.03 TB
G&P Piston
Systema PSG1 200% spring

[Flak]

If I remember correctly, the CA SR-25 has an extended V2 gearbox which, due to the similar necessary compression ratios required for an upgraded AEG projectile velocity, requires a longer spring to do so. A normal M120 is not long enough (while it may take some squeezing to install, not nearly as the normal spring probably) to apply as strong a force towards the end of the firing stroke as a PSG1 spring would, simply because of its length.

[Paladin101]

Classic Army uses an extended Piston in addition to the extended gearbox. You need a CA25 piston.

[Mack]

Sorry I didn't make that clear. It's a G&P extended piston for an SR25. All the parts that are proprietary to the CA SR25 are in there.

[Paladin101]

I'm still thinking the problem is the G&P Piston. The fact that G&P's design is different than CA makes me believe that they just don't go together well. If you have the original piston you could compare them to verify they right dimensions and confirm 100%.

Only other thing I can think of is that you have a bad air seal on the hop up unit. Have you wrapped the bucking in a bit of teflon tape and make sure you tapped the barrel back after install?

[Mack]

Compared before I installed it. Wanted to make sure that it was compatible. The pistons are the same length. The teeth come to more of a point than the CA one. The CA is also quite a bit softer than the G&P.

[110]

Try using the King Arms Hop Up unit or the madbull ultimate, they both have orings that in theory keep compression even and prevent areas of air to "escape." I know tight bore barrels usually give higher FPS slightly, maybe a 6.01/6.02. Stay away from the JBU ones, It's 6.01 after teflon coating and as more rounds go through it, the teflon erodes creating an uneven/bigger bore barrel than advertised.

If PSG1 spring doesn't do the trick, put the O ring from the piston over the cylinder for a good 10 minute s to expand it a bit, do the compression check with piston + cylinder assy. and make sure pressure is good.

The other thing to check is your gears. Are they the same teeth ratio as the stock CA ones? The CA Sector ( the one that engages piston) has more teeth to compensate for the other pair of teeth it engages on the piston, but I'm sure you know this already. Just asking because I haven't run across CA SR-25 Helical Gears, either out of stock or I assumed they never made em.

Lube Up the metal cylinder head nozzle and the nozzle attacked to the tappet plate. When they engage/bump ugly/safe sex demonstration, it should be smooth and the compression should be consistant with the super lube/dense grease you apply inside the area the two engage.

That's all I have, I'd get a new gearbox if I were in your shoes.

[Paladin101]

Good points 110. For the O Ring put it in a small cup of power steering conditioner fluid overnight, revitalizes the rubber. You can throw in the seals from your GBB pistols mags as well. It's good for them.