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Technical Q: A&K M249 Hop Up upgrade


ECRRRainman

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So I am aware of the commonly reported shortcomings of the A&K M249 hop up chamber and of the "bic pen" fix, but I curious if other newer aeg hop up mods can be used on an M249.

 

For starters, I would like to hear suggestions on the most recommended replacement bucking to use with the M249.  I havent been in the loop for years and there seem to be multiple different types of buckings. I am also curious, after researching things like flat,G, and R hop ups, are any of these viable options for the M249?

 

I had an idea of installing a new "no lump" or smooth bucking and seeing if I could place a shaved down "m" or "v" type nub (or even a small flat piece of plastic/eraser) above the barrel window and allowing the original vertically placed M249 nub press down on that to allow for more contact with BBs inside the barrel.

 

Has anyone tried anything like this on an M249 style hop up with success? Am I putting a whole lot of thought into a mod that will result in little benefit? Id hate to have my SAW be outranged by other aegs that have these sort of new hop ups installed.

 

Thanks

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I've had good results with Maple Leaf buckings in M249/M60/PKM-style hop ups. Last MG I put a Maple Leaf 70 degree bucking into was chrono'ing around 365 fps, and it was hitting targets at 70 yards (measured with Google Maps) with .25 bbs without lobbing.

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I don't know if they (A&K) ever fixed the hop up chambers, but on the earlier models (2008ish) they had a special bucking as the hop ups internally weren't quite right - the CA ones where the solution if you wanted to use a regular bucking or do a mod - a couple of people on here were using grub screws to hold the barrel and on a Japanese forum someone was removing the bucking lips and replacing with an o-ring.

 

I'm also thinking of r-hoping my 249, but I do think the hop will need a fair bit of modding to get it to use it properly (given that ideally you to want to push down as much as you can) or a completely new hop up chamber.

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From what I can tell the A&K hop up is identical to my prior CA M249 para (nub drops in vertically rather than horizontally like o the hop ups)

 

After some googling the only thing I can see as a potential purchase solution is a custom hop up unit made by a guy called Black Wolf over in Russia I believe.

 

Hop-Up M249 A&K:

 

This hop up looks to use an arm to lower the nub horizontally like other hop ups.

 

The problem is I can't find the hop up for sale on their website and I'm currently waiting for a reply to their contact email.

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As others have mentioned, I prefer to track down a Classic Army chamber so I can use standard buckings, but that's mostly for convenience and to deal with feeding issues.  My accuracy fix for the M249 is to remove the bump on the bucking, Dremel out the tiny nub hole until it accepts a soft Firefly buffer rubber: 

 

SDC10915.JPG

 

Then carve a new arm out of hard plastic:

 

SDC10914.JPG

 

SDC10917.JPG

 

I did this one a couple of years ago, and it still puts a big smile on anyone's face who shoots it.  

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Thanks. It was meant to be a prototype for some 3D printed arms, since we have several SAWs (plus PKMs and M60s) that could use better hopups, but it worked so well the first time I tested it that I haven't messed with it since except to clean the barrel.

 

The main tool you need is a Dremel, with cut-off wheels to enlarge the barrel window and extra thin diamond bits to square it off:

 

 

http://m.harborfreight.com/diamond-point-rotary-bit-set-20-pc-69653.html

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I wouldn't mind doing that if I had the equipment to machine things out cleanly, but despite having Dremeled dozens of barrel windows I don't think my end result is clean & pretty enough to please picky customers.  Still, I should probably model the hop arm, since there are at least four guns on the team armory wall that could use this mod.  

 

I'll probably redesign it to use a bit of rubber sheet instead of the FF buffer rubber; it's a great part but not really necessary if you're making your own arm.  

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So instead of starting a totally new thread I figured I would add on to this one.

 

I was fiddling with my A&K Mk46 and I noticed the inner barrel and hop up unit has the ability to rotate while installed into the gun. The small "tab" at the bottom of the hop up will align with the GB and if I try to rotate it clockwise (looking from the front of the barrel) the tab will not turn as it catches in the GB like its supposed to.

 

But if I turn it the other way I can rotate it about 10-15 degrees. I have not yet been able to test fire it to see if there are any issues but I would assume if it can even feed properly the hop up will curve BBs to the side somewhat.

 

Has anyone else had a problem with a hop up unit rotating inside their M249?

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While working on our team Mk46 I noticed that as well. I also noticed that the hop unit has another tab on the top side, which aligns with a slot on the body of the gun. Would it be possible to create some locking mechanism for the hop unit?

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I was able to track down the developer of the hop up unit in the video I posted and found a shop that stocks and sells the newest model.

 

0409151701_zpslulsflkz.jpg

 

0409151702_zpsiyhzchhh.jpg

 

It was a bit tricky since the site is in Moscow but they were able to ship it to me.

 

Next I need to get it installed and see how it does!

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I grabbed it at www.airsoftsports.ru

 

I had trouble with the page translation so I emailed their customer support and they set up the order for me.

 

With shipping it was ~$80

 

Before I found this Russian retailer the developer informed me he sent a batch to Redwolf airsoft to sell but I haven't seen any news from them.

 

Edit: I attempted to throw my original barrel into the New hop up and discovered the stock hop up bucking does Not seat well in the new hop up unit. I assume this is because the stock bucking is shaped differently than other aftermarket and standard aeg buckings (doesn't have the traditional feeding lips)

 

I'll be ordering a New bucking and nub today. Maybe I'll try out this flat hop I jeep hearing about

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Edit: I attempted to throw my original barrel into the New hop up and discovered the stock hop up bucking does Not seat well in the new hop up unit. I assume this is because the stock bucking is shaped differently than other aftermarket and standard aeg buckings (doesn't have the traditional feeding lips)

 

I'll be ordering a New bucking and nub today. Maybe I'll try out this flat hop I jeep hearing about

 

Judging from the photos, a "true" flat hop will require enlarging (lengthening) the hole in your new chamber.  This might be a drop in solution, if it feeds:  http://www.airsoftgi.com/product_info.php?products_id=11712

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I looked at that bucking/nub combo bit I've read mixed reviews about Modify parts so I gave it a pass. I did pick up a maple leaf concave nub since I figure it will potentially offer more contact with a bb than a flat nub.

 

We'll see how it goes hop ups are a bit foreign to me and I'm learning what I can

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I've used the Ryusoku soft set in a few oddball guns that I didn't feel like Dremeling, like a Cheytac, with acceptable results.  I think that (like the Prometheus flat bucking) they had some feeding issues in M4s.  A shaved purple bucking is more forgiving.  

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