A&K M249 Upgrade Nightmare

Discussion in 'Gun Building, Modifications & Repairs' started by Valkyrie64, May 30, 2019.

  1. Valkyrie64

    Valkyrie64 New Member

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    So last thanksgiving I got it into my head that my A&K M249 needed some upgrades. My thinking was "It's a beast stock, imagine what it'll do with some upgrades!" The upgrades were extensive and expensive (see list below for the parts I added). I didn't do the work myself, I'm not experienced at all, let alone enough to do something like this. Now, 6 months later, the damn thing hasn't worked since. From the very beginning it was a charlie foxtrot. Broken gear shafts, lack of sufficient battery power, wiring issues, feed failures, poor air seal. Some of those are even repeat offenders, but most have been resolved. Currently, the gun works, but it keeps snapping gear shafts, typically after less than a thousand rounds. The problem is that the gears sit crooked in the stock gearbox shell, and the high torque / high speed motor keeps snapping them like twigs. The techs I paid to do these upgrades are good, they do far more extensive upgrades on a regular basis, so I don't think they are to blame. I also had another tech take a brief look at it, and he say the gear problem as well. The problem is most likely that the gearbox shell is a POS, and the holes that the gear shafts fit into are actually crooked. I've looked everywhere online, and it seems that the general consensus is that the A&K M249 gearbox shell is generally of pretty decent quality, so I'm at a total loss as to what the heck happened. Does anyone have any idea what I can do? I was looking at getting the Matrix CNC M249 gearbox shell offered on Evike, but its been out of stock for months. I'm don't know if anyone can actually tell me anything that can save my gun, but I'm pretty desperate right now. I have never posted anything on forums right now, so if I did something wrong, tell me but don't attack me over it.

    Upgraded Parts Added:
    AIM Top Hellfire High-Speed Piston w/ Metal Teeth
    Lonex TITAN Motor - High torque & high speed
    Krytac 8mm caged steel ball bearings
    APS Polyamide Explosive Bearing Piston Head
    Bull Gear CNC M249 Hop-up unit
    Prometheus Purple Hop-up bucking w/ nub

    Also Changed:
    Wired for deans w/ MOSFET: Using 11.1V LIPO
    Replaced Tappet plate
    Most gears have been replaced by now as well
     
  2. fred_ditto

    fred_ditto Well-Known Member

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    If push comes to shove, there is always the Retro Arms gearbox shell. Stay away from anything matrix/angel custom/other assorted evike house brand.
     

  3. Honeybadgerz17

    Honeybadgerz17 Well-Known Member

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    People sell old gearboxes sometimes used. Also I think evike sells a stock gearbox for cheap enough.
     
  4. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    As the resident "expert" on these guns, I'm willing to bet your primary issue is your bearings. The M249/60 gearbox cannot use any old bearings, they must be the ones that come with the gearbox or an available upgraded version, but any standard bearing set will not work because they do not sit properly into the gearbox openings for the bearings. Could you post a picture of the gearbox opened up, with the bearings in place? Or if not, at least a link to the bearings you had installed.
     
    kazuchan likes this.
  5. fred_ditto

    fred_ditto Well-Known Member

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    Do FLT bushings work?
     
  6. Valkyrie64

    Valkyrie64 New Member

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    Interesting. The new bearings not sitting right makes a lot of sense. I didn't intend originally to replace the bearings, but the stock ones were about to catastrophically fail. If I hadn't decided to upgrade the gearbox when I did, the next time I went to the field with my gun, the bearings would have broken free and shredded all my internals as they ricocheted around inside my gearbox. To prevent this from happening, I spent the money and went with what I had always heard was the good stuff: Krytac 8mm caged steel bearings (click the name for the link). As for pictures, I don't have my gun with me right now. It will be a little while before I can get photos.
    If your right, and its a compatibility issue with the bearings, this is great news. It means I can buy the $100 A&K M249 gearbox set from Evike and salvage the shell and bearings from it. It's a hundred bucks I'd rather not spend, but if it gets the thing working, its money well spent. I'm not going to get my hopes up just yet though. Every time it looks like this gun might just work and I get optimistic, the darn thing laughs and says "Nope".
     
  7. fred_ditto

    fred_ditto Well-Known Member

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    Or, you could just look for M249-compatible bushings and not have to spend $100 on the extra gearbox. On second thought, though, it's not unheard of for people with 249s to have a spare gearbox...
     
  8. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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  9. Valkyrie64

    Valkyrie64 New Member

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    Having some extra spare parts would definitely be good, but I'm mainly considering the whole replacement gearbox because at this point I probably need a new shell anyway, since this thing has broken and then gotten gutted nearly a dozen times in the last 6 months. I'm not certain, but I also think one of the things that the techs did to try and get the gears to sit correctly was attack it with a Dremel. I say attack because working on this thing is like waging urban warfare. Plus, the only way to be certain bearings will work with an A&K M249 gearbox is to actually salvage them from another A&K M249 gearbox.
    Upon searching for replacement bearings, I have discovered that, once again, my options for fixing this gun are severely limited by a lack of compatible parts that are actually in stock somewhere that's not overseas. Does anyone know any place that has any in stock with a reasonable shipping time?
     
    Last edited: May 31, 2019
  10. Honeybadgerz17

    Honeybadgerz17 Well-Known Member

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    I do maybe... lemme look around on my work bench. Not gona use them so just pay shipping and they're yours. I just took some bushings from another gun I had and attacked them with a dremel. Been working for me for several thousand rounds, so dont see the reason to switch back.
     
  11. Valkyrie64

    Valkyrie64 New Member

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    Wow that's very generous of you. Luckily you're just across the puget sound from me, so shipping costs and times shouldn't be bad. You wouldn't happen to know if these bearings will work in an M249? I haven't been able to determine yet if A&K M249's use standard 8mm or proprietary 8mm bearings. There isn't any form of agreement on the matter as far as I can tell.
     
  12. Honeybadgerz17

    Honeybadgerz17 Well-Known Member

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    Good for you to know that the bearings are from an A&K M249;). I can pack and ship them on Wednesday when I'm off work. Should be about $7 with USPS priority.
     
  13. BoogerMc

    BoogerMc Airsoft Jedi Master Supporting Member

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    Last edited: Jun 1, 2019
  14. LightIsRight

    LightIsRight Well-Known Member

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    Hmm, I got a bearing that looked like that without the lip when I bought my used G&P M16. Interesting, I dodn't know what it was for. I think the seller had a PKM so it was probably from that.
     
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  15. Valkyrie64

    Valkyrie64 New Member

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    Thank for the help everyone. With a little luck, most of my problems will be resolved by swapping the bearings out. but if this gun has taught me anything, its that nothing is ever this easy, so please keep throwing out suggestions, because odds are I'm not out of the woods just yet. I won't know for sure for at least another week and a half. Stay tuned to this thread though. I might need some more advice in the future.
     
    Last edited: Jun 1, 2019