Cursed Gun or Negligence?

Discussion in 'Gun Building, Modifications & Repairs' started by wetpee, May 12, 2021.

  1. wetpee

    wetpee Active Member

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    I don't have this gun with me anymore but it still kills me thinking about it and I really want to get this one back and get it sorted out at some point. This guy is awesome and has been one of my most appreciative and understanding clients and still comes to me for work.

    I recommended a set of parts for the guy and he threw it together himself or maybe had someone else do it since I was busy with other guns by the time he finally got all the parts together and he didn't want to bother me to rush it before his big game he had coming up. He used it for a day or two and brought it to me for an FPS bump the week before the game. He was getting 310 on .2g and wanted it as close to 350 as possible and based on the parts he got, I thought it was strange he wasn't getting at least 340.
    G&G ARP9
    Full Lonex compression kit from Brill Armory
    Guarder 110 spring
    SHS full steel rack piston
    SHS 13:1 gears
    Prowin hop up unit (not my recommendation)
    Prometheus 128 mm inner barrel (recommended ZCI -- wasn't available)
    Rocket 22TPA motor (I recommended ZCI -- wasn't available)
    Maple leaf Omega Nub
    Maple leaf Super Macaron bucking 60
    GATE TITAN Advanced
    A few parts were substituted for similar spec parts because he was in a rush to have it done. I wasn't consulted about the substitutes, but I think they're negligible to the end result and the ultimate problem that occurred.
    Upon opening the gearbox, I found that absolutely nothing was greased and his stock bushings were worn enough to let the axles wobble slightly. I also noticed the Lonex CH was the newer version with the padding on the front (not what was pictured in the listing on Brill), which I was a little skeptical about because of the reports about the padded Maxx heads shearing CH posts, but I hadn't heard anything about the Lonex ones being a problem so I left it in. I cleaned and lubricated everything and put in some fresh steel bushings. Swap the Rocket motor to a ZCI 22tpa I had in stock because the rocket sounded like **** and was drawing more amps than what I usually get with the ZCIs. Back together again and running smooth, lower amp draw, but it chronod high. I short stroked 2 teeth and it was bang on 350 fps on .2g BB.

    He goes to his big event and it gets through day 1 with no hiccups. Next day at the event it chronod like 250. ****. At least it wasn't misfeeding lmao.
    I get it back and go through it and find slight damage to the cylinder head posts as well as the mounting holes on the CH. FML.
    chdamage.PNG
    Airseal is still bang on, but I also find some odd damage to the hop rubber like the lips are hanging out of the chamber too far and the BBs are wearing a little ramp into the lip. I go pick up the stock barrel and chamber set from the guy and try every single combination of the 6 parts. No changes. I sand a spare confirmed good hop rubber ever so slightly one bit at a time and keep chroning after each bit of material removed and no changes until finally it chronos like 150 and it's not sealing. New rubber, and then sand a confirmed good nozzle by the same process and I get it up to 290FPS. I polish the piston and tappet tracks in the gearbox to ensure there are no hang ups anywhere and continue to inspect everything. No weird scoring on the nozzle. Everything seems to be aligned. I replaced the CH with an SHS one and it fit and sealed great and worked well with the nozzle. Tried replacing the piston o-ring and spring with confirmed good parts. No cracks in the body, BUT he's got a new 10" handguard on that's not fitting all the way against the receiver. Inner barrel was still the same and either the original outer barrel or the extension he put on wasn't allowing a longer barrel through. I take a look and the barrel nut is just too short to reach the receiver and the threads on the receiver have cracked off a chunk, still holds fine though and everything is centered. Just in case, I remove the rail and nut for further testing and brace the barrel assembly by hand, being sure the chamber is seated flat on the front of the gearbox and the nozzle is sealing to the rubber. No change. I figure the damage to the CH posts could be throwing off alignment ever so slightly to cause a problem so I rebuild and reshim the whole gearbox into an unused Lonex shell. I had to custom fit the Lonex shell to the ARP9 and it fit great in the end. Get it all together and I think I gained like 4-10 FPS on average. At this point I'm at my wits end and I try a Lonex tappet, Guarded tappet, SHS tappet and try it with and without tappet delayer to no avail. I had the intention of not charging the guy at all for the work since I figured I did something to **** it up. I ask that he give me $50 for the lonex shell and call it quits as I'd already been in a depressed state before this whole fiasco and the whole time I'm doing work on his gun, I'm only losing money in parts I can no longer sell as brand new, can't take on anymore jobs because I already have 2 customer jobs on deck, losing all confidence in myself as a tech, and I have 2 of my own replicas that I wanted to do some tests with, one being my first DSG build I had yet to tidy up and take to the field.

    What are the chances the body of his gun is just barely fucked up enough to not allow anything to work? Could the SHS cylinder head or something else be slightly messed up from the damaged posts in the original shell? I only put like 20 rounds through it with that CH and it looked totally fine. Could there be damage that's just not visible to the naked eye and could that really account for 50+ FPS loss? I'm so lost on this one but I really want to get this figured out. I'm generally quite good with machines and diagnosing issues and this is the first of about 30 guns I've worked on that has had such an elusive problem. The only things I didn't do were test it in another body or up the spring power but I didn't have any extra bodies laying around and I'm not keen on solving an obvious FPS issue with a stronger spring. The cylinder I used was over-volumed for the 128mm barrel with the intention he could use .2 or .25g BBs at 1.1j and joule creep closer to 1.49j with .3 or .32g BBs when he takes it outdoors. I tried chronoing with .3g and it hardly gained any energy. Did I miss something or this gun just cursed? Literally any suggestions are welcome. Thanks for reading if you made it this far. You're the real soldier.
     
    Last edited: May 18, 2021
  2. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    The ARP9 has one unique feature that you touched on and is my suspected issue.

    >>>The 128mm barrel.<<<

    It should be around 150mm

    Nipping the barrel by 1" and your FPS will drop.

    This AEG runs a stock M120 to get you about 330fps, this is to mitigate PME with 11.1V

    Up the volume of the cylinder and the FPS will drop.

    This is due to the pressure wave changing to a longer impulse, what happens now is that your bb has left the barrel before the full wave hits.

    If you take a stock ARP9 and install and cover a 375mm barrel in the AEG, it will hit 400fps with stock components.

    We discussed it here:

    https://www.airsoftsociety.com/threads/new-to-as-and-a-few-questions.161741/page-2#post-1825453

    So the simple way to get the FPS up in a stock ARP9...add in a longer barrel.
     
    Last edited: May 12, 2021
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  3. ma_airsoft

    ma_airsoft Well-Known Member Supporting Member

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    Personally, my guess is on the short stroke. swap the sector and rechrono would be my first move.

    Hard to say what the best option would be without the gun in front of me but if i tested compression and had no issues I’d probably look at tappet timing and mag feeding more closely.

    I think we’ve all had a gun that we just cant get right. its part of the process. Low fps seems like a totally solvable one though if you can get creative like you did.

    also, whats the titan settings set to? precock off please. have seen weird setting combos cause weird issues with the gun

    E/ the shs HT is actually 16tpa not 22. thats most likely why it draws more amps
     
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  4. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Off on a tangential topic...TPA does not definitively define it's level of AMP draw.

    Back in 2010 I actually had an AEG motor dyno and various motors hit varying amp draws with varying RPM's.

    While I did not open the motors and count the TPA...I can extrapolate that motor capability is not just by TPA alone.

    Example: These two motors have a near identical RPM

    Eagle Force EF1300 - Long Type

    RPM - 27500
    Amp Draw - 1.55 AMPS
    CONS - 7.5
    Noise - Mild, a louder harsher dentist drill type noise.
    Heat - Mild, warm to the touch
    Result - A great motor, very efficient due to it being hand assembled, but is it worth the price around $85.00. Good motor to reference the TM EG3000HC.

    Ares/Shooter, Super Torque - Long Type

    RPM - 26100
    Amp Draw - 3.61 AMPS
    CONS - 25
    Noise - Mild, but of a different pitch, more of a thump type of pitch.
    Heat - Mild, warm to the touch
    Result - A definitely a super torque class motor. Magnet was very strong, hard to turn by hand, could be a cousin to the G&P M170...but this one works out of the box and at a lower cost over the G&P.

    One is a ferrite and the other is a neo magnet motor.

    And then compare it to the TM EG3000HC motor

    TM EG-3000HC (High Cycle)

    RPM - 32800
    Amp Draw - 2.92 Amps
    CONS - 3.5
    Noise - Low, it hummed with a slight pitch that reminded me of a dentist drill.
    Heat - barely warm to the touch.

    Which is also a ferrite motor, but more speed and higher amps.

    http://forum.mnairsoft.org/viewtopic.php?f=59&t=28181&p=280528&hilit=Motor+speed+cons#p280528

    Thus that is why TPA alone is really a guideline...and can be vague at that...

    And for a note. The voltage was set at 9V, the maximum that the unit could put out.
     
    Last edited: May 12, 2021
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  5. wetpee

    wetpee Active Member

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    @ma_airsoft Yeah I turn everything off on the ETU's for testing. It was also my impression that the rocket motor would be the same spec as SHS but it was advertised as 22TPA (on evike probably). I thought it was plausible they could have done some motors with more winds on the armatures but I do honestly think it was 16TPA. Had ports in the can which was cool but didn't give the performance I wanted. Higher amp draw and not quite as snappy in semi. Very in line with what I expect of SHS HT.
    @Guges Mk3 Wow just report me now I was literally involved in that thread. I probably neglected to calculate voluming. What would you consider a type 2 cylinder? I've heard a bunch of different ways to refer to the port locations I can't retain it. Type 0 and 1 are pretty straight forward but i feel like there are so many different variations after that.
    Why would it get the 350 at first and then suddenly lose 100 FPS? This is what was troubling me and perhaps most heavily influencing my bias to conclude that the gun was fucked. Maybe there was a problem at first? Tappet getting hung up allowing air to leak until the peak amplitude of the wave hits and then after enough cycles it wore material down to move more freely?
    If he wants to have the option to use .3g BBs for outdoor use what would be your recommendation? The OB length he's going for now is under 10" so that when he has his little acetech or G&G tracer unit tracer installed, it just barely hangs out of his 10" handguard aboot a 1/4". He was previously using an extension on the stock OB and the longer IBs wouldn't fit through it. Opted not to modify as I didn't have the proper tools to do a clean job and had already lost my confidence with this thing.
     
    Last edited: May 18, 2021
  6. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Report? What? Why?

    Type 2 is classically 2/3 of the way back from the Cylinder Head.

    To drop 100 after one shot means something was seated or became unseated after the first pressure wave (shot). I think you are on the right path.

    .30...well looks like he wants to Joule Creep...then over voluming is the best way to do that.

    As for extensions not working...seems to be tolerance issues.

    But, he has a really short barrel and the AEG needs to have a really short high peak pressure wave.
     
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  7. wetpee

    wetpee Active Member

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    Hahaha I was just joking around being mean to myself for not remembering that thread.
    It wasn't just one shot. At the very least he chronod at the field (presumably at least 3 shots), and then went through an entire day of play and he didn't seem to notice any loss of power. Next day of the event is when he chronod 250.
    I'm pretty confident the short stroke isn't a serious issue here. Yes, this would reduce the amplitude of the pressure wave, but in terms of the performance we're shooting for, it is desirable and there are plenty of ways to work around that loss, and I think that loss is very minimal. I've done SS2 on m110 three times now and the other two came out perfectly at the desired 350 fps +/- 5 and maintained it.
    To clarify, that variation is between the two builds, not the variation within each build. Any custom builds or compression upgrades I do, I shoot for +/-2 fps, try for less if it's DMR/sniper, and can almost always stay within +/-3 fps with the usual tuning, making sure parts function well together and check seal before and after lubricating.
     
    Last edited: May 18, 2021
  8. wetpee

    wetpee Active Member

    166
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    Libertyville
    Been updating him with the info you guys have given me and it looks like I'll be getting the gun back soon and I'll do some more playing around with cylinder volumes. I have quite a variation of cylinders to use now that I didn't before. Perhaps we can compromise on being able to use .28g BBs for outdoor play or just say screw it and stick to .25g.
     
    Last edited: May 18, 2021
  9. wetpee

    wetpee Active Member

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    Update: He's been able to achieve 327 +/-3 FPS on .2g BB with a 247mm 6.03 prommy barrel and some orange hop rubber he had lying around. Krytac perhaps? Still need further testing so I will continue to update once I have the replica on my desk. It may have a type 1 cylinder so we might still be overvolumed.
     
    Last edited: May 18, 2021
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  10. ma_airsoft

    ma_airsoft Well-Known Member Supporting Member

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    Why would the barrel not have had a drop from the beginning? Your volume shouldnt have changed between day 1 and day 2.
     
  11. wetpee

    wetpee Active Member

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    Libertyville
    @ma_airsoft I'm a little confused what you're talking about maybe I misspoke. I haven't had the replica in my possession for over a month and I don't have footage of the most recent work I did after it came back to me after losing 100 FPS since the first time I worked on it. I'm going to edit some of my previous posts here for accuracy as I begin to recall things a little better. This post will sum it up well enough for now until I get the gun back:

    When I gave it back to him the first time, it was a type 1 cylinder, Lonex 2x o-ring cylinder head with front pad, guarder 110 spring, no AOE correction, SHS 13:1 gears SS2, lonex o-ring nozzle, prommy 6.03 128mm IB, prowin hop unit, Maple Leaf super mac 60 rubber with omega nub doing right at 350 +/-2 FPS on .2g and then dropped to 250 the second day he played with it.

    The thought process of the higher volume cylinder was so he could use heavier BBs if he wanted to take it outdoors and get legitimate range gains via joule creep. I was unaware of all the effects of over-voluming at the time. I don't think I even did the measurements and calculations to be honest. None of my research at the time had showed me anything about having FPS loss from over-voluming so I thought it was a perfect application to over-volume in hopes that he could get ~1.1j on .2-.25g BB and then get closer to 1.49j on .3g or .32g for outdoor rifleman, but it would seem I very grossly over-volumed or the 128mm barrel is just too short for properly tuned SSG AEG.

    When he brought it to me the second time, the ultimate changes it received were (possibly) type 2 cylinder, lightly sanding the nozzle, Lonex GB shell, Prommy ms110 spring (in case the guarder spring could have lost some power from pre-cocking), and stock G&G hop unit, rubber, and nub because the ML had the weird feed lip damage and then I trashed another ML trying to modify it to avoid the same feed lip damage.

    Since then he's put in a prommy 6.03 247mm barrel getting the aforementioned results. It's either type 1 or type 2 cylinder I can't remember if I changed it or not.
     
    Last edited: May 18, 2021
  12. wetpee

    wetpee Active Member

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    Added this photo to the OP of the damage that was found when I received the replica for the first time. Note that there is both damage to the inside of the shell as well as the Lonex cylinder head.
    chdamage.PNG
    The mounting holes in this updated Lonex CH are ovular and not perfect circles as is typical with nearly every other CH for standard gearboxes. I'm not sure how to feel about this but perhaps it actually prevents the damage that is known to happen with the front-padded MAXX CHs.
    Perhaps some polishing around the CH posts is needed with the Lonex front-padded CH.
     
    Last edited: May 18, 2021
  13. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Your picture is too small for me...just FYI.
     
  14. aotsukisho

    aotsukisho Well-Known Member

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    Those are likely for both V2/V3 compatibility in the same part, ZCI cylinder heads I've used have the same thing.

    Note that the holes/pegs are not meant to provide a locking interface, they are just there to align the cylinder head in the gearbox. It should not be a tight fit, the impact should transfer to the front of the gearbox not the pegs.
     
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  15. wetpee

    wetpee Active Member

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    Its a thumbnail Guges click on it make picture go ZOOM
     
  16. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    I did, but the resolution looks to be about 1024x800

    Being that the view below is as large as it gets (pulled a link from your host for image). I can't make out the small details...but that's just me. Hey, I have similar mat...except I have some closing slots.

    [​IMG]
     
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  17. wetpee

    wetpee Active Member

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    Ah my bad I just used snipping tool on a downscaled window of a 1080p recording and exported in whatever file format it defaulted to. Anyway, the outside edges around the alignment holes on the cylinder head are warped like it was getting knocked perpendicular to the direction of the piston movement. Then it seems the resulting ridges on the CH dug into the gearbox shell around the posts.
    Nice I think I got this one on AliExpress ~$14
     
  18. Squad144

    Squad144 Active Member

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    Ocean Springs
    Sorry to bring back the thread or really turn it into something else by accident... but... I found this picture. Talk about a cursed gun to whoever puts this in their gun!
    [​IMG]

    For all those who do not know what I am talking about, take a closer look at where the port on that cylinder is located.:D
     
    Last edited: Sep 23, 2021
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  19. OutlawAirsoft

    OutlawAirsoft Active Member

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    Oops. I recon they'll get maybe 45 FPS out of that thing.
     
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  20. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    I say 18 fps. Depending on barrel length.

    I have fixed many a mechbox that was put back together by techs who had "2 Years of Experinece" by doing that...plus the guy that thought you could AOE a mechbox with 2 piston heads and get a better seal. He screwed one onto another with a fine thread metal screw and nut....I have to admit his drill work was "nice", must have had a press.