G&G CM16 Carbine FPS reduction

[BrightCandle]

The site I am playing on has a hard limit of 328 fps. According to everything I read before I bought the G&G CM16 Carbine it should come out somewhere around 290-328 fps, at least that is its designed performance. However having fired some shots at targets I was slightly concerned it was a little hot and took it to a range to get it checked out and its firing at about 335-340 fps. I have spoken to the site and they are telling me I have to reduce it below 328 fps.

 

Am I right in thinking the default spring in the CM16 is a G&G M100? Is reducing to say an M80 the best way to go about reducing the FPS or should I be considering a different modification (inner barrel etc) instead. I want to make the minimum adjustments possible to get it firing within requirements, do so ideally as cheaply as possible (since the gun was only £100) and be confident after the change that it will chrono below that FPS. I have about 2 weeks to get it fixed.

 

(Hi by the way, lurker but first post!)

[Monty]

Get an M90 spring, it should fire just over 300fps.

[Mack]

If you want to do it cheaply, just clip one coil off the spring and that should get you down enough.

[straffham]

If you're not happy dismantling the gearbox you could try filing the air nozzle down a fraction to reduce the air seal?

[BrightCandle]

I replaced the spring, went from whatever was in it (assumed M100 from what others have said) down to a G&G M80 and velocity has definitely dropped. I will have to go and get in chronographed again but I suspect I am now below 300 based on the sound and impact volume. Might have to either clip my existing spring or get an M90 spring from someone else. Gun is now shooting low, at 10m its 3 feet below target and no amount of hop up corrects it. Its even low at 5m with maximum sight adjustment by about 2cm, so its not exactly playing ball right now!!!

[dex]

I wouldn't put anything less than a m90 in it. You really shouldn't need to.

[BrightCandle]

I changed the spring from the G&G M80 to a SHS M90 and its chronoing (same model, different unit) of 327 FPS. Which is right no perfect. I was expecting a larger reduction but I am happy with that. Cheers for the advice, even if I didn't follow it initially :-)

[BrightCandle]

And after I put 3000 rounds through it last night (that was a very heavy fire game, was all on semi and just 3 hours of gameplay!) FPS has dropped to 316. I am assuming this is just a bit of initial part wear but if it goes much lower it looks like I could go back to the M100. Sigh.