G&G cm 16 fps dropped by 55fps please help

Discussion in 'Gun Building, Modifications & Repairs' started by plasticnoob, Jul 29, 2015.

  1. plasticnoob

    plasticnoob Active Member

    587
    94
    hidden city
    When I first got the gun it shot at 330-340. I did a compression mod(cylinder head+cylinder non ported) no o ring. When I went to shoot it last it shot at 280ish and I knew something was wrong this was 2 weeks ago.

    This week
    I just installed my new hop up, barrel tight bore plus I added a brand new o-ring seal into the piston which I tested the compression and it was greatly improved. The old one had terrible compression. The new o ring works amazing and gives 90%+ seal.

    I got it chrono t his week and the new results are on par with what I had before I installed the barrel, hopup and oring. around 260-280


    I am not sure if my compression mod somehow is failing because there is NO cylinder port hole like the factory stock one, or if my spring is somehow bad, this has about 15-20,000 rounds through it now. I am not sure if an spring can drop 50+ fps?

    What do you recommend?
    my first thought is to replace the old parts because the cylinder had a port to let air/in out. Maybe not enough air is sucked in?



    *note I removed the grease off the piston and piston head, does that have any affect? I thought it was meant to be clean and not dirty, the o ring did get 10wt silicone oil placed around it.



    I will have the gear box open tomorrow I am working on a shim job

    also is there a wrong way to install a spring? maybe I installed my spring backwards
     
    Last edited: Jul 29, 2015
  2. Rogers

    Rogers New Member

    55
    0
    Houston
    There are a lot of things that can cause power losses. I'd first ensure that your build has a proper combination. What barrel length do you have?

    Like I said...There are a lot of things to check, I'd just check to make sure the parts agree with each other on paper first.
     

  3. ThePinballWiz

    ThePinballWiz Member

    616
    2
    Buffalo
    How long is your inner barrel? It sounds like it is short but you have a full cylinder so your air volume to barrel is wrong.
     
  4. stjimmy1500

    stjimmy1500 Member

    67
    8
    Bloomington
    In your first paragraph, do you mean the new cylinder head you put in did not have an o ring around it? That would be bad...
     
  5. XSolarFantomX

    XSolarFantomX New Member

    233
    0
    Grosse pointe
    It is the compression or the spring
     
  6. plasticnoob

    plasticnoob Active Member

    587
    94
    hidden city


    my bad, I ment, I installed a NEW cylinder + a head.

    the piston that came with the gun had a green o ring, it was very bad system. I replaced it with a new oring that is black and it works perfectly..







    I think it might be the spring, I heard the G&G springs are weak... I will replace all the parts with the old compression to check this week and report back saturday night.




    the new inner barrel is a 229mm the old one is a tad longer, by a half inch if that.... So I would say the factory is 225mm or so. Both cylidners are the same size, I bought an M4 cylinder, just there is no porting on it like how my factory one has. Just a full cylinder no holes. I thought this could be a problem?
     
    Last edited: Jul 29, 2015
  7. Rogers

    Rogers New Member

    55
    0
    Houston
    Called it. Build not good on paper. That barrel is a little short bud.
     
  8. XSolarFantomX

    XSolarFantomX New Member

    233
    0
    Grosse pointe

    Barrels don't do anything unless it's specially ported cylinder look in to that
     
  9. XSolarFantomX

    XSolarFantomX New Member

    233
    0
    Grosse pointe
    Check you Spring pm me for more Info
     
  10. Rogers

    Rogers New Member

    55
    0
    Houston
    He is using a barrel intended for a ported cylinder and installed a full one...how does this not mean anything? An out of balance volume ratio can certainly have an effect on power output.
     
  11. Rushin

    Rushin Well-Known Member

    3,920
    32
    Kalamazoo

    Yup, he's right. Although I've never heard of power loss from overvoluming...
     
  12. plasticnoob

    plasticnoob Active Member

    587
    94
    hidden city
    Like I said in the OP even after changing the barrels results are the same. This happen after I did the compression mod the first time before I replaced the o ring and before the new hop up plus barrel
     
  13. Rogers

    Rogers New Member

    55
    0
    Houston
    Did you replace the cylinder for a full one during the compression "mod"?

    http://forums.airsoftmechanics.com/index.php?topic=11308.0
    You certainly can lose power due to improperly balanced ratios. Here's another big study...
    http://www.airsoftmechanics.com/index.php?topic=12693.msg151361#msg151361
    It's very common actually.
     
  14. Rogers

    Rogers New Member

    55
    0
    Houston
    A different way to say it might be...
    DSG users run short barrels for the same reason DMR builds run longer barrels. Not necessarily for accuracy, though this seems to be the usual fallacy followed, but for power optimization.

    Put the ported cylinder in, doesn't take but a second. If I'm wrong I'll eat my shorts. :D
     
  15. DreadCo526

    DreadCo526 New Member

    315
    0
    Sylvester
    um yes you will need a half volume for that setup you can drill the holes your self just make sure you dont leave burrs and that you drill at least 3. the non ported cylinder is also a big deal so change that or you could drill the holes for this also, exactly how the stock holes are. that should fix any air seal problems you may have.

    if you like what i said you could give it a like to help build up my rep thanks!!
     
  16. Rushin

    Rushin Well-Known Member

    3,920
    32
    Kalamazoo

    Seriously? You'll build up your rep by not asking to get likes. Likes do absolutely nothing.

    Since he swapped out the unported one he can just drop the old one back in.
     
  17. plasticnoob

    plasticnoob Active Member

    587
    94
    hidden city
    i did, had no clue this would have an effect to be honest. I bought one knowing it was rated for m4 and it's hard to even find one with "cylinder holes" I guess I could drill later.
    The stock cylinder head and nozzle was quite leaky.

    Going to reinstall my old cylinder with new cylinder head and report back next week ounces it's all done, chornoed
     
  18. plasticnoob

    plasticnoob Active Member

    587
    94
    hidden city
    Okay the last chornoed was 265-275 using the new cylinder non ported. I replaced the cylinder with factory one Thad ported brought my fps up to 295-305!!!!! Man that sucks lost 30+ Fps from thcylinder.

    Now to figure how I loss the other 20-30fps!!! From factory 330. I even tested the old hop up + barrel. It yelled a difference 5+_ Fps. I think it's time to replace the factory spring to get back to 330fps.

    I doubt I bother with it now. I am happy I'm back to 300fps and if it drops 10 Fps more then I'll hanged spring. This shoots close to 230 feet now!!! I was hitting a target at 220 feet. Quite impressed
     
  19. Lust

    Lust New Member

    138
    0
    SF Bay Area
    What length is the barrel? What brand of parts are you using? Did you lubricate your compression parts properly? Did you check compression properly?
     
  20. plasticnoob

    plasticnoob Active Member

    587
    94
    hidden city
    Barrel is same as factory just a tight bore.

    Se I used lube and grease

    Compression was 100% with lonex parts but switching back to a ported cylinder I got weaker compression and it leaked slowly as I pushed the piston in even with the new cylinder head. Nothing I could do. It was worse with the stock parts.

    I could dermal a port on the new cylinder someday and see if that helps.