M249 DSG build

Discussion in 'Gun Building, Modifications & Repairs' started by Zaryk, Jan 20, 2016.

  1. Zaryk

    Zaryk Well-Known Member Supporting Member

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    I'm putting together a list of what I'll need to build a second gearbox for my m249. I want this gearbox to be a high speed setup, so I'm planning to do a dsg setup. I just need opinions on the items I'm buying and if they are worth getting or if I need to find a higher quality part in its place. Here is my build list.

    What I already have.
    M249 gearbox
    Siegetek dsg
    Shs tapped plate
    18:1 gears (xyt or Shs, I have both)
    Burst wizard 3 (newest model with micro switch protection, hardwired not plug n play)
    Metal spring guide (polished)

    What I plan to buy.
    Shs brand-
    14.5t piston
    Shim set
    Bore up kit v2

    Lonex brand-
    Pom lmg air nozzle
    A2 short torque motor

    Everything else-
    Modify 8mm tempered steel bushings
    Sorbo 3/16 70d bore up
    Neo pad 1/32 70d
    20a micro switch
    M160 spring (zci maybe? Not sure if that brand spring is any good but heard good things)

    My goal is 45-50 rps @ 300 fps. I may buy a new set of 13:1 gears later if I'm not happy at that speed but for now I just want to use the parts I have to get it up and running and go from there.

    My M249 is a Para model with 363 inner barrel so I chose the bore up parts to help insure I'm not getting under volumed after I short stroke the piston.

    I know most of you are going to say not to use the burst wizard, but I'm not flexible here, I've only had good experiences with them and unlike what is said about them they do offer trigger protection if they are hardwired. Especially the newest model which has micro switch protection, which is exactly what I need.

    Before I'm asked, I'm experienced working on gearboxes and know about high speed setups. I'm building this gearbox separately from the original so I can swap them out to suit my needs for different games. My box mag is upgraded and wired to my trigger so it should have any issues keeping up with the feeding.
     
  2. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    You can skip out on most of the bore up parts tbh. Getting 300FPS out of a DSG is pretty easy, although I would avoid ZCI springs like the plague. Really, really bad QC, your more likely to end up with an Mlolacmlotto then whatever you want.
    13:1 gears do not mesh with DSG's(I'm assuming the M249 uses normal V2/3 gears, not V6/7, correct me if wrong). 18:1, or Riots 14:1/ 10:1 are your only options for the DSG. Due to Riot making the gearing change between the bevel-spur, instead of all other gearsets making it between the spur-sector, you can't drop in 13:1's. 16:1's fit, but the ROF difference is pretty negligible.
    Modify is fine, although Lonex bushings are just as nice, but might be cheaper, I don't recall exact prices.
    I also don't recall for sure what setups hit what RPS's, but 45RPS with 18:1's and an A2 seems off to me for some reason. One of the stickies has some rough RPS guidelines, check them out if you haven't already. Regardless, I would suggest swapping out the A2, its going to run hot and eat brushes like all Lonex motors. SHS or ZCI, unless you want to drop the cash for an ASG, which were holding their own pretty well last I heard.
     

  3. TheInfidel23

    TheInfidel23 Resident Derp Supporting Member

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    Also, assuming you've looked inside an LMG gearbox shell. The A&K generic models at least.

    If you have, you would know that normal bushings don't really work.

    If you even want to replace the stock bearings, you'll need SAW gearbox specific ones
     
  4. Zaryk

    Zaryk Well-Known Member Supporting Member

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    Thank you, this is exactly the kind of info I was seeking.

    I'm just aiming for the 45ish rps, if I don't achieve it I can always fine tune later as this build isn't going to bring my M249 out of action, so I'm not rushing it.

    I shouldn't get under volumed if I don't use bore up parts on a 363 barrel?

    What spring brand would you suggest?

    M249s are v2 compatible.

    Lonex bushings are half the price of modify, so thanks for that tip.

    I'll track down the shs/zci motor, and I'm betting it will also lower my build cost.

    Again thank you, that saved me a good bit of cash, and I really appreciate it.
     
  5. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    Check out Legacy's post right above mine. I have no experience with the M249 gearbox, so if he says you need M249 bushings, then you need M249 bushings.
    Yeah, you will undervolume some, but you will have no issues hitting your FPS goal(300 is pretty low for a DSG, or rather should I say, very attainable) and... well.. its an 249. I have a feeling that super pinpoint accuracy isn't a huge concern.
    Prommy. Haven't gotten a mislabled spring from them yet. Guarder should also be pretty on point from what I have heard. For more ACMlotto, but less price, SHS. Also, (IMHO)always better to buy high, and trim it down if need be, then buy low and have to space/buy another. Spring trimming isn't for everyone however.
    Brill/Cland both have selections of SHS/ZCI(HT,HS, and balanced). Look up roughly what TPA on 18:1's(and I'm assuming an 11.1) will hit your goal, then find the appropriate motor.
    And of course, Brill and cland for even more price savings.
     
  6. Raven1st

    Raven1st Well-Known Member

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    SHS springs loose a lot of FPS very quickly.
    Both of my SHS springs lost 30fps after 1k cycles and settled after loosing 45fps.
    One was an M120 and one was an M130.

    If you are running a HS setup this is not ideal as it will lead to a large change in piston return times after little use.

    Buy Prommy and stay happy.
     
  7. Zaryk

    Zaryk Well-Known Member Supporting Member

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    The 249 takes standard v2 8mm bushings. I'm aiming for 300fps to keep me viable on my field so I can run full auto in the villages and make my MED fairly close so I don't really need to run a backup gun. I intentionally made kept my gun quite inaccurate for suppressive reasons so accuracy is of absolutely no concern to me. I also have built my list of parts strictly from Brill and clandestine be cause they are the best in my opinion. And yes, I'll be running 11.1 lipo with a high discharge.

    Thanks again for spending your time helping me on this.
     
  8. TheInfidel23

    TheInfidel23 Resident Derp Supporting Member

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    If it's a para model, you have an A&K. And if you have an A&K M249 SAW gearbox, it takes proprietary bearings. Please feel free to post up pictures of what shell you feel Tm bushings will fit into, because if the designed has changed recently, it would be a huge improvement.

    However, the current design uses bearings like these, and to use standard bushings would be catastrophic.


    Also, got mistaken for legacy. +1 to me.
     

    Attached Files:

  9. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    Hahaha, I'm just not used to seeing you post around here that much :D
     
  10. Zaryk

    Zaryk Well-Known Member Supporting Member

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    It's a replacement gearbox I'm working on and not the original. I bought the lmg used and I can guarantee it's not any new designs as this thing is definitely older, at least 5 years old if not more. I'm pretty sure it is the classic army version, but it doesn't matter much because the original gearbox is long gone and very well could be the A&k gearbox shell in it now. It used to be owned by the owner of my local field and used as a vehicle turret. It has some rust and a whole lot of wear to the finish and you can tell it's from use and not "antiqued". I'll double check the bushings in the shell to be sure which I need. Thanks for the heads up.
     
    Last edited: Jan 21, 2016
  11. Airborne101

    Airborne101 Well-Known Member

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    You can determine if it is a Classic Army M249 by the black gas block (A&K are white/silver) and it should say the brand right behind the trigger.
     
  12. Zaryk

    Zaryk Well-Known Member Supporting Member

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    OK, thanks for the info. This one is a mix of both it seems, it has the A&k gas block but classic army markings. It's kind of a Frankengun. I kind of figured it was after talking to the previous owners. I couldn't track it back to the buyer, but the last three owners were all fairly good techs.
     
  13. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    I'll add my two cents in here for what it's worth, the trigger switch in these guns is not as suseptable to the same issues as say a V2 or V3 switch, they really do not require additional protection such as a MOSFET, etc. However, it is advisable to replace them with a higher quality switch than those offered by Airsoft retailers. I provided a link to such a switch in my M249 rewire tutorial found in my Engineering, tricks, and tips thread (see the link below). Otherwise, hope this helps.
     
  14. TheInfidel23

    TheInfidel23 Resident Derp Supporting Member

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    Microswitches really shine in a MOSFET setup though ;)

    What you say is true, and not having semi automatic to deal with is a huge reason why.
     
  15. Zaryk

    Zaryk Well-Known Member Supporting Member

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    But since my box mag is wired to the micro switch, I feel better with the mosfet in place.
     
  16. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    My boxmag is direct wired as well, other than adding a resistor and a diode, I've had no issues running without a MOSFET. However, running with one has caused me nothing but trouble. Ive fried every one because of excessive heat from prolonged full auto.

    Check out the discussion in this thread.
    http://www.airsoftsociety.com/forums/f10/m249-mk-1-upgrades-110376/
     
    Last edited: Jan 22, 2016
    -Spitfire- likes this.
  17. Zaryk

    Zaryk Well-Known Member Supporting Member

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    I've run this mag without a mosfet too with no issues. It just eases my mind. I also wanted the functions the burst wizard offers. Some fields around my area restrict rof during certain matches (mostly milsims) and with the burst wizard I can adjust my rof exactly to the field limit. Also I kind of like using it for my lipo low battery alarm and cutoff instead of using the annoyingly loud plug and play alarm I have. It also has the resetable fuse, which is nice to have but not really a reason I put it in there. I have a few reasons I chose to use it. But I do agree with you that it isn't necessary to run one in this setup.
     
  18. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    If I am understanding you correctly, you've already been using the MOSFET in this gun, if that is correct, then you're one up already because you haven't had any issues, that's good. If you're planning on doing g a quick swap gearbox situation, might I suggest using an additional plug on the gearbox switch for both gearboxes so you don't have e to mess with your wiring each time. Literally a plug and play type of situation.
     
  19. Zaryk

    Zaryk Well-Known Member Supporting Member

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    Yeah, I've been using a mosfet in it for a year now with no issues. I was thinking the same thing with the wire harness. Would you use a deans plug or something else? I really don't want to add any more resistance than I have too, and I don't mind picking up a new style plug if it's going to be better than deans.
     
  20. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    Deans would probably be your best bet since you only need two connection points. Deans will not add enough resistance to make a difference since most of the ones I've seen are gold plated and gold offers very little resistance.