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A&K MK43 now upgraded. Getting alright at this!

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Heya gents. 


Purchased an A&K MK43 recently. The externals are pretty quality though poorly put together, The iron sights don't quite line up. But not a problem with an LMG! 


I replaced the original useless hop unit with an AirsoftPro one, and now lifts bbs pretty well up to .30's. However it only read at 260FPS. I had to figure out whether it was the spring or the compression. Having read the stock seal being pretty bad I felt it would be good to crack open the box and replace all the compression stuff and the spring at the same time. 


I purchased an FPS Air compression set, these parts are ultra light fancy made in Italy aluminium alloy stuff, made to high tolerances and very colourful. They do make some stuff for some weird guns (I have a set for my ARX160 to put in at somepoint). The set includes a Piston head, Cylinder Head and Air Nozzle. I bought an SHS/Rocket 14.5 all metal piston and a SHS full cylinder. 


I haven't ever taken apart an LMG gearbox, and only taken apart a V3 and V6 before. 


Once I managed to work out how to get the thing out I was surprised about how many screws there were and how heavy and robust this thing was. This shell aint ever going to crack! You can see all the gears working through the hole at the bottom. 






Took out the original spring, it was similar to the other A&K stuff, weak and shorter then average.




I tested the compression, and although fair I could see that some gear lube had got on the piston head and piston somehow. Probably eating away at the plastic. 




Took out all the old parts, cleaned up all the green, brown and black snot lube. Put some quality lube on the gears and they span freely with the original shims and ball bearings, no changes needed shim wise. Gears were stamped A&K and seemed fine. 




Put together the new all metal 14.5 tooth piston, piston head, full cylinder (Which to be fair the original was just as good), Cylinder head and the new O-ringed aluminium air nozzle. The compression was good, but not great. The long air nozzle really doesn't do much favours, still better then the original though. 


Stuck a low rated M95 spring in. I thought about changing the motor, but the only motor I had was a JG Ferrite high torque, which actually had the exact same magnetism and design as the stock one so no point in changing, its clear the motors were both made in the same factory. This is something to change in the future. 




The Anti reversal was a real pain on this gearbox but managed to get it in. Tried to fire up the gearbox with a battery directly to the contacts, picked the wrong ones and the microswitch started to smoke. Fearing the worst I tried the next two pins and it seemed to work fine. Might have to replace the switch at somepoint! 





Switched the connectors over to deans and chronoed. 




RESULT! ~340 FPS, needs to settle down but is fairly consistent. It's slightly quieter then before, the RPS is a bit lower then before because of the stronger spring (I Suspect the original was an M80). However I am dead proud of being able to do this first time with no massive issues. The LMG gearbox was certainly the easiest one to work on so far, though the anti reversal latch was more of a pain then standard V3 boxes. 


I am certainly getting better at this malarkey! Next project is to open up my ARX160, replace the air seal stuff, install mosfet and tighten up some loose bits. Cant wait to take this LMG out on the field though! 



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So after the sector gear lost two teeth on the spur side I had to install some new gears. The A&K stock sintered ones are known to be quite bad so went with the ZCI Advanced 18:1 set. 



With the stock shims the sector gear was pushed up by the high spur gear so much that it ran at an angle, So shimmed the sector higher. Its not perfect but it's fairly good!

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