M249 MK-1 Upgrades

Discussion in 'Gun Building, Modifications & Repairs' started by Nukenstan, Dec 7, 2014.

  1. Nukenstan

    Nukenstan New Member

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    Hello everyone. Let me start off by letting you know I've done a ton of research already. Okay, so now lets start.

    I'm looking to upgrade my M249 that I've just acquired a few weeks ago. I'm trying to achieve a medium-high ROF (not insane, but better than most) and an FPS of about 410-430. NOT ANY HIGHER. I know some people think that ROF on a support gun is a bad idea, but the way i see it is with everyone running around with fully automatics, the only intimidation you will get from a stock LMG is from size and looks. If you are down range and BBs are hitting everywhere around you faster than most, and you hear a mini-gun rip from afar, you really want to get down. Besides, you've got to take advantage of the huge mag size anyway ;). Also, the reason I want a high FPS setup is because (I play mostly Field) I want to be able to rip through the bushes and trees. You will really need to focus on finding better cover if the bush your hiding behind is worse than cardboard. OK, so here is the list I've put together. Let me know what you guys think and if I should switch anything out (please put why if you do).

    - Madbull 509mm 6.03 inner barrel
    I've used these barrels in 3 of my builds now (KWA m16, DBOYS Scar L, KJW M700) and they have worked beautifully. I'm pretty set on this barrel, but recommendations and why would be appreciated.

    - Guarder 70% Hop Up bucking
    I've only switched out a stock hop-up once, that was in my sniper build. I could really use recommendations on this. Keep in mind I'd rather have reliability over accuracy in this since I'll be throwing tons and tons of BBs. Also, I know the nub is proprietary so should I try buying a new one or making my own out of a tile spacer? (Made one for my sniper out of tile spacer and it works better than any other nub I've encountered)
    http://www.evike.com/products/25889

    -Systema M120 Irregular Pitch
    I've heard systema makes pretty darn good springs that don't really get that FPS loss over time, and are very reliable.
    http://www.evike.com/products/26259

    -Lonex TITAN A3 Short-type
    I've heard tons and tons of great things about these Lonex motors for quite some time. High speed and is apparently good up to an m140 spring.
    http://www.evike.com/products/43102

    -Modify Shims
    I feel this part is the most overlooked part in the gearbox. Everyone states to shim it, but with what? These are apparently stainless steel (as apposed to zinc/copper which create shavings). Of course this will be accompanied with re-greasing. Recommendations here would be much appreciated
    http://www.evike.com/products/28929/

    -MAG m249 box mag
    I'm finding it really hard to find reviews on this. I had their Vietnam and stanag midcaps in the past for my KWA m16 and they worked flawlessly. The one thing that concerns me on this is the lack of auto-winding. Although this isn't a huge deal as I plan on hard-wiring this to the guns motor so that every time I shoot, it feeds.
    http://www.evike.com/products/29267

    -Guarder Steel 16:1 Gears
    Steel gears to handle the stress. I probably wont be buying these right away unless I need to. I've read that the stock gears are fine.
    http://www.evike.com/products/28258/

    -Bearings
    The gearbox comes with 8mm bearings. I beleve they are proprietary so I wont be replacing these unless I need to.

    -Battery
    This is the hardest part for me. I can not figure out which battery to use. I would like a 9.6V with the maximum Mah I can get (being an LMG, everything needs a large capacity, even the battery.) If everything went my way I would use a 9.6 5000 Mah brick battery, but there is not enough space in the handguard for that. I dont want to hang it in a pouch on the side. I've read about people converting it to fit in the box magazine, but it does not look like it could fit a brick type in there (not tested though as I sold my M16 with the brick a year ago). If anyone could let me know it works that would be awesome because I dont want to buy only to find out its useless or I'll just have to hang it. Also, if I'm getting the MAG box mag it wont fit anyway, but if the brick type does work in the box mag I'll just use that and ditch the MAG. I know nun-chuck batteries work in it. I was thinking about going Lipo, but not sure I want to go the 11.1 route, though some do have great Mah (not sure if they will fit)
    http://www.evike.com/products/33443/ http://www.evike.com/products/38346/
    http://www.evike.com/products/24487/
    On the other hand I have found some 9.6v, but still unsure whether or not they'll fit
    http://www.evike.com/products/29557/
    http://www.evike.com/products/29054/
    I know for a fact that this will fit because I've tested it. I'm probably going to go for this unless one of the others will fit.
    http://www.evike.com/products/24483/

    Thanks a ton for any help you can offer :)
     
  2. Airborne101

    Airborne101 Well-Known Member

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    Your build list looks good, just a few things though.

    The reality of Systema springs is just about the opposite of what you have heard. They are actually known to break. On top of that due to their design, they start off very hot, and then will settle to their advertised range. So an m120 may put out 440fps at first, and then settle to 400fps. Not a good choice for spring IMO. Personally I like Madbull and Prometheus, however I have used SHS with success in the past as well.

    What you consider "medium" ROF is really what will dictate your motor, gears, and battery choice. With a 9.6v and your listed motor and gears, you are looking at the 25rps range. I know a Lonex A2 will do 20rps on 18:1 gears, and you are going with a lower ratio and higher speed motor. Heck, you might push 30rps with that setup.

    If you want to fit the battery in the handgard, then lipo is the way to go. RC lipos are small and have great capacity. Go to hobbyking.com and look around at their lipos. They have a ton of different sizes and capacities. On top of more sizes, they are also going to be much higher quality and lower price than "airsoft" lipos. Case and point: http://www.hobbyking.com/hobbyking/...00mAh_2S1P_20_40C_LiFePo4_Receiver_Pack_.html More capacity and less than half the price of either pack you linked.

    If you decide the Nimh route, then go to EliteAirsoftBatteries.com and get one from there. Tones of options. And Elite cells are the best cells out there for airsoft, not to mention they are usually cheaper than airsoft retailer batteries.
     

  3. Nukenstan

    Nukenstan New Member

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    Thanks Airborne101 for the help!
    Around 25RPS is what I'm looking for, in fact that'd be perfect. Thanks for the link to the website. I've looked around and found a couple LiPo's, an 11.1V and a 7.4V, both 20C and 5000Mah. I'm guessing I should go with the 7.4V if my ROF is going to be insane with what I've picked, but what do you think?
    http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=15006
    http://www.hobbyking.com/hobbyking/store/__8578__ZIPPY_Flightmax_5000mAh_2S1P_20C.html

    Also, since going with a LiPo i should probably get a MOSFET installed. Would installing it to the M249's V7 gearbox be the same as installing it in a V2 gearbox? The reason being is that I plan to do it myself through the help of youtube videos. What MOSFET would you recommend?

    Again thanks so much for the help!
     
  4. Airborne101

    Airborne101 Well-Known Member

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    Either lipos works, but yes, you want a 7.4v.

    And yes, you can install a MOSFET in the gun although with a 7.4v, you don't necessarily need to. That being said, I install MOSFETs in all my guns regardless of battery. Because the M249 uses a microswitch, you will want to use a MOSFET without active breaking. So just a simple fet. If money is no factor, Extreme-fire would be my first choice. If money is a factor, then this should do quite nicely: http://www.clandestineairsoft.com/e...t-pcb-protected-low-resistance-fet-p-571.html
     
  5. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    I would not recommend the MOSFET installation as of this moment because evwery one that I have ran in my 249 has fried due to excessive heat. You could try this.

    http://www.evike.com/products/34840/

    I will be swapping a similar version of this into my 249 within the next few months. It uses an automotive style relay and therefore should be more than adequate for any lipo, including an 11.1v. However, I also recommend swapping the trigger switch for a better quality one. The factory switches are junk.

    Check out this thread for more information on upgrades and a discussion between Airbourne and I on the MOSFET issue.

    http://www.airsoftsociety.com/forums/f10/m249-mk2-recommended-upgrades-109951/

    Hope this helps.
     
  6. Nukenstan

    Nukenstan New Member

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    Thanks! I think I'll just go with that better switch that Booger recommended since its way cheaper. If that doesn't work I might as well give the MOSFET a try, but that's if it doesn't work. I plan on replacing the box mag motor with this one http://www.tamiyausa.com/items/mini-series-40/racing-motors-43050/jr-atomic-tuned-motor-15215 OR this one http://www.tamiyausa.com/items/mini-series-40/racing-motors-43050/jr-hyper-dash-3-motor-95025. Do you think it would be able to hand direct current from the guns motor itself, or would I be better off be replacing the 2AA with a 9V?
     
  7. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    I have my boxmag wired directly to the gun's wiring harness, when I pull the trigger, the boxmag feeds. Save your money, the boxmag's stock motor works just fine. I'll post some pictures of the internals of my gun and boxmag once I get a chance to, probably this weekend. I'll be a bit busy until then, my computer took a dump on me last week and I'm still in the process of restoring it. In fact, I may have lost nearly a year's worth of files if I can't recover them.

    In the meantime, check out my Monster 60 and Ongoing Projects threads, one of them has a wiring diagram for the boxmag/gun harness.

    Airbourne, sometime in the next month or so, I'm going to try that double stacked MOSFET idea we discussed, but I have to get past a few other projects first.
     
  8. Airborne101

    Airborne101 Well-Known Member

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    I don't think that is going to solve your problem. You'd have to change your firing style to reduce heat. If you don't give it time to cool down, you'll kill the MOSFET, whether you use 1 or 2.
     
  9. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    I was thinking much the same, but I would still like to give it a shot. LOL.

    Sad part is, I seldom use my 249. It's usually Rhino on the 249 and Overkill on the MONSTER 60. One of these days though, I'm going to say it's my turn.
     
  10. Nukenstan

    Nukenstan New Member

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    Alright, thanks for all of the help! I will definitely take a look at those other posts! I hope you are able to recover at least a portion of your files, I had my SSD drive crash on me in a power surge earlier this year and I lost a ton of progress.
     
  11. Nukenstan

    Nukenstan New Member

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    OK, so I put all of the upgrades in and everything worked flawlessly. Except for the barrel, which spews out bbs all over the place. like every now and then one BB will go straight (not very fast though, maybe 200FPS) but 99% of the time they go like 3-5ft and are spewing out of the barrel in a 45 degree angle in random directions like a shotgun. I think it might be the "suck back", but it doesn't make sense because its the same length and all, just tighter. I know its the barrel because I've taken only that out and it works fine. Absolutely no defects in the barrel at all.
     
  12. Airborne101

    Airborne101 Well-Known Member

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    It's not suck back. Suck back can not happen because the nozzle disconnects/breaks the seal with the bucking after each shot. And if you are using a ported piston head, air can also get in from behind the piston head. At most there is a loss of force, but there is no "sucking" action.

    Regardless, that wouldn't cause your issue. Your issue sounds more like a bucking/nozzle/feeding. Check to make sure the bucking is seated on the barrel properly, and then when you install it into the chamber it doesn't get bunched up. The bucking lips should make a circular shape in the chamber and be even. If it's misshapen, it will cause issues. Similarly, make sure the bbs are pushing past the bucking lips easily (but not without giving it a little nudge). I had issues with Prometheus hard buckings where it require quite a bit of force to push the bb past the lips, and that cause feeding/fps issues.
     
  13. Str8Oper6n

    Str8Oper6n New Member Supporting Member

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  14. Str8Oper6n

    Str8Oper6n New Member Supporting Member

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    Maybe even some micro heat sinks for computers on the mosfet and a micro/nano fan to spread air across.
     
  15. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    Nuke, try swapping your original barrel back into the gun. I have heard several SAW users complain that tightbore barrels do not work well with these guns. In fact, an AS member mentioned once that they got the best performance from a 6.08mm barrel because the extra space in the barrel allowed the gun to "spew" bbs much faster. Don't know if this is true or not, but it's worth a shot. I run the standard barrel in mine and it spits like a dragon. I've recorded distances of 250 feet and still have enough energy to feel the hit, not bad, but still feel it.

    Be sure that when you replace the hop up bucking into the hop up unit you oil it up good with silicone oil, the M249 units can be quite tight and will often cause the bucking to slide out of place. Also be sure that everything is lined up correctly. There is a ridge inside the bucking that must line up with a groove in the barrel. If these do not align, it will cause issues. Same with the hop up window in the barrel, be sure it is on top when you reinsert the barrel and bucking into the hop up unit.

    When I must disassemble and reassemble mine, I oil the outside of the bucking only. This creates some friction between the metal barrel and the rubber bucking to help prevent slippage, but allows the bucking to slide easily into the hop up unit.

    Sorry I haven't had a chance to work on the gun lately, but I may be able to get to it sometime this week, but don't quote me on that, after all this is Christmas week and things get kind of crazy around here. I will post something though, just as soon as I get a chance.
     
  16. Airborne101

    Airborne101 Well-Known Member

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    You're gonna have to explain that to me because I'm not following. A larger bore will create a bigger air gap around the bb, which in theory improves accuracy, but I don't see how it would shoot bbs faster. If anything, velocity drops with a larger bore since you have more blowby.

    Im not trying to attack, but that just seems like an odd mechanism to throw out there.
     
  17. Nukenstan

    Nukenstan New Member

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    I did replace the stock barrel back in the weapon (I kept the aftermarket bucking) and skirmished it today and it worked flawlessly in terms of feeding. And when I had the TBB in there I visually inspected everything while installing it in the hopup and before it was placed in back in the weapon. I did try adjusting the hopup when it was in the rifle and it went from broken sprinkler to a large outflow pipe, if that makes sense.

    I may not be the most experience tech out there, but this is not my first time working on an airsoft rifle. I just cant figure out what is going on with the barrel. Like I said, barrel length is the same. I'll try throwing it in very carefully tomorrow and see what happens though.
     
  18. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    As I said, I don't know if the statements are true, but to venture a best guess, the additional air cushion around the bbs allows them to flow through the barrel easier. Consider this, if a tight bore barrel decreases the air cushion by reducing the distance between the bb and the barrel; it stands to reason that the potential for drag is increased because the potential for impact against the barrel also increases. Therefore, for a gun that spits bbs at a higher rate of speed, the potetntial to slow down the velocity of the bb from impacting the barrel and thus creating drag also increases.

    However, if the likelihood of impact is reduced by increasing the aircushion by enlarging the inner diameter of the barrel, it stands to reason that the bbs would flow easier through the barrel by reducing the potential for impact against the barrel. Therefore, a loose bore barrel would allow the gun to fire faster with less issues. So, in essence, it doesn't increase the speed of the gun, but it allows the faster gun to maintain speed and consistency by reducing the potential for drag.

    As I said, my best guess. Doesn't mean it's right, but it does make sense.
     
  19. Airborne101

    Airborne101 Well-Known Member

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    But generally speaking, tight bores increase FPS, due to the decreased gap and thus reduced blowby. So even if the decreased gap means the bb contacts the walls/bounces more often/more friction, it is still flying out faster.

    So essentially by what you are proposing, you would have to have a measurable drop in FPS with a tighter bore, yet we regularly see a measurable increase in FPS.
     
  20. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    As I said, just a guess. However, I'm wondering if his cylinder to barrel volume is the issue. If he's running a full cylinder on a short barrel, he could be over voluming his barrel, which will also cause a loss in velocity as the bb exits the barrel because the extra air affects the bb by rushing past it and thereby creates drag that can alter the bb's flight.

    There is also the possibility of a bent barrel, even a slight bend will cause issues. I had a similar issue with a friend's gun, his barrel had a slight curve in it and it was causing his bbs to go awry as they exited the barrel.

    Anyway, Nuke, hope you figure it out and when you do, let us know. By the way, no offense was intended earlier, but I generally explain things in a simple manner in case the recipient is not versed in Airsoft tech, one must generally assume this posture when answering questions as we get more newbies than anything else.