Currently I can not stand the run away gun issues that I am having, basically the cheap trigger switch is not bent right, so when you pull the trigger it fires and release the trigger it still fires, and continues to fire and fire and fire some more while you curse the thing out while being pelted with BBs because its is continuing to fire and players still think you are in play and not taking your hits because it won't stop firing, sheeesh! So arise old post from the dead while I update the repairs for this issue.
The A&K/Echo1 M249 is the exact same replica. They are both 100% compatible with the Classic Army M249s but not exactly the same.
The are some excellent post on these replicas at ASF and arnies especially Far east's M249 review. at Arnies.
My A&K M249 is a fairly recent purchase of mine but at $180 shipped from E hobbies asia I could not pass it up. I have done a lot of researching and lots of players in my neck of the woods use this replica. I do not have enough field time to do a proper review but I am going to reference some things I have seen first hand so please bare with me.
First impressions, one large Operation type game of play. (incidentally I was yelling arnie quotes and acting like a general loonie when this pic was taken at op Prometheus glory. "Get into Da CHoppar"

This replica was much heavier and surprisingly longer and bulkier to lug around the field than my M60E4 , part of the day I actually carried both of them due to feeding problems which I'll address in a moment.
I have been in contact with over 12 individual A&K and echo1 M249s and they all chronograph different! Mine chronos 330fps with .20 another one right out of the box chronoed 385fps and the third was 410fps all with the same .20 gram BBs. All were right out of the box that day. This tells me that either the factory is using up what ever left of springs they happen to have or there is a serious consistence problem in production. Regardless this is not a big deal as it is very very easy to change out springs.
One of the very cool features of this mechbox is the quick change spring.
Open the feed cover.
Then unbolt thread the thumb screw near the stock and bull the pin out, this will pivot the stock down the below image show where the pin and thumb screw are, note the hole at the rear of the receiver.


Press this button down once the stock is rotated down. then press the round part in the back of the mechbox body. This will release the spring guide allowing you to quickly and easily change out your spring to adjust fps to filed limits. You may want to upgrade the solid lump of aluminum that is your spring guide to one with a bearing on it as it will reduce stresses in your gearbox and may increase rate of fire a scotch.


Do NOT do this on the field. After changing a spring you should re chronograph this replica to make sure that you fall in the games fps limits and adjust your minimum engagement limits appropriately. Failure to do this can get you thrown off fields, get SAW replicas banned from certain fields (this HAS happened already) or killed by other players when you are shooting a HOT gun.
Oh and just like the real M249, mk46 or FN MINIMI as it is also called. This replica will also feed from M16/M4 family magazines. I have tried MAG, CA, TM, JG, G&P and Echo1 magazines with no issues thus far.
It it is also very easy to change out the bucking and inner barrel as the whole assembly pops out with a press of a lever. Another known flaw is most of these replicas come with a totally nonfunctional hop up. This is because the nubbin is miss formed and does not have a impact on the bucking. It is easy enough to replace the nubbin with a piece of wire insulation, alternatively you can use the ink reservoir of a BIC ball point pen to source a new nubbin to replace the old one. Several players local to me have been disappointed with the inner barrel quality, I am with holding judgment until I get the hop up functioning a little better
Below is the description I got from a guy in our group:
"I got the fix for you
I did it with mine after have the same problem
First disassemble the hop up and take out the rubber nub or what ever you want to call that thing (by the way mine was ripped as well)
Replace the piece with the plastic tube found in a standard pen(cut to same size as rubber piece) Try that first then if need be make plastic tube a smigg bigger about 1mm maybe even less than 1mm. but try the same size first because you don't want to go to big as it will block up the barrel. I would recommend giving the end that contacts the bucking a little sanding to deburr with a nail file so it wont rip the bucking
also after you get the hopup set make with a sharpie that location on the outer wheel and the hopup chamber
Try that.
It took me about 5 min. and increased the range by about 25 to 30 feet "
Currently my hop up has two setting worthless and jammed, I am going to fiddle with making a nubbin while I wait for a new CA hop up chamber.
Batteries, fit either in the fore grip on PARA or ranger versions or in the stock, below is a pic I got from google images that shows the difference between a Clone stock and CA stock, (verified by comparing them in person at the last op. As you can see the CA stock necks down a little less and there for will take a bigger battery, they are completely compatible with each other. My end cap will not stay on as the BB indent that is supposed to retain it does not put up enough force to retain it, I just duck taped it on.


This image is taken from a on line army manual. It shows how the sights adjust. My suggestion is to set your hop up for the average range you engage targets at and then adjust the sights to match up.

There are some well documented issues with these M249 clones, Which include. Faulty trigger switches, which are easily fixed by re bending the contacts or simply replacing them with a CLASSIC ARMY replacement. It is common on any support replica to eventually have burnt contacts, you can avoid this to a extent by not laying on the trigger for so long or think about upgrading to deans connectors and/or MOFSET switches that handle current better.
Feeding issues which have been solved by Killbucket who has marketed a replacement feed spring and has a how to make your own FAQ on DIY version full instruction his site using McMaster-Carr # 966K49 spring and McMaster-Carr# 3038K192 silicone tube. regardless any machine gun replica is sensitive to BB quality. You are feeding so much ammo through it so rapidly that jamming on a malformed BB not only caused a stoppage in your cover fire but may have jammed things up enough to damage the mechanism of your box magazine or mechbox. Currently mine does not feed reliably, I have been told by another user to look in the box mag his feed wheel had quality issues inside that may be causing it. I have not had a chance to screw around with mine yet. I ordered a CA box mag so it is a back burner project for me. Below is a image of my M249 replicas box magazine compared with my surplus Real steel (blank) M249 box magazine for reference.
On my box mag the lid is taped on because during the game it popped off with the loss of 3000BBs and much bad language uttered.

This is the EVIL orange birdcage flash hider. not only is is ugly, and incorrect but it is cheaply made and glued on. My best suggestion for removal is to first unscrew the outer barrel form the replica, Then dip it into nearly boiling water. Then wrap in in a towel and clamp it into a bench vise. and use a gentle but firm turn with the biggest pair of channel locks you can get your hands on. If that does not work you may try some glue debonder sold a a hobby shop or failing in that cut it off with power tools like a dremel and delicate use of a e xacto knife. Mine did eventually turn off. with the hot water and a big wrench method. Also shown in this picture is the This is the “Gas Collarâ€