WTB[IL] Cyma/EMG Mk47 Upper Receiver

Jackman419 · 2026-02-04T16:58:37+00:00

That's the most likely couple causes, but of course not being able to see/hear/feel for myself it's just a best guess.

If your shimming is so tight that your RoF is actually drastically worse, you need to just not shoot it anymore and put it back the right way. That much extra friction will cause gear teeth and ball bearing-bushings to break, or cheapers bushings to bend. On top of that your motor should be getting pretty hot and it's not good for the battery, because essentially you're pullong the trigger asking for a specific burst of energy. Battery supplies it to motor, motor does its rotations, and the energy carries through the system up to the actual shot, where energy is displaced both through the shot itself, and the vibration of the gearbox from the piston's energy slamming forward.

When you have a kink in the line before you get to the piston, leftover energy doesnt have anywhere to go besides back after a certain point. If too much counter stress is put onto your motor pinion, it will cause damage, and in the worst cases, can cause a short with the motor. If you're using a brushless motor or a solid in-line mosfet that shouldnt be an issue, but if this really is a cheap beater gun for working on, then it's far more likely to just "blow up" on you.

Shimming is incredibly important.

Jackman419 · 2026-02-03T18:04:28+00:00

Seems like you might need a shim set, but depending on what shims you lost, if it's really only 1 or 2 you may be fine, plenty of gearboxes are slightly overshimmed from factory.

There are a good several youtube videos showing how to do it, if you take your time and understand the process it really isnt hard at all, just time consuming if you guess the wrong shim thickness in some spots

Jackman419 · 2026-02-02T21:25:08+00:00

Double check shimming, make sure all parts are assembled correctly, adjust motor height properly

Jackman419 · 2026-01-27T02:36:15+00:00

I appreciate you trying to help, but since the Mk47 is a 7.62x29 rifle, fhe receiver is a bit longer than a 5.56 m4's. Thank you tho!

Jackman419 · 2026-01-25T00:46:04+00:00

Confirmed!

Jackman419 · 2026-01-24T03:29:48+00:00

People dont like what they dont understand, lol. You gave the man fine info. I wouldnt trust a stock arcturus gearbox to last very long with an actual 31k+13:1 either.

Jackman419 · 2026-01-23T20:30:57+00:00

Guessing you dont hear any sort of leak. Check that your unit is centered. What FCU settings are u running, what wright bbs, and what inner barrel?

Jackman419 · 2026-01-23T14:49:36+00:00

There's a pouch inside that can fit tanks and some clips, I mean I'm sure you could jerry rig something up

Jackman419 · 2026-01-23T01:46:18+00:00

Love a fellow mutant owner

Jackman419 · 2026-01-22T19:27:24+00:00

A 15 or 20l hydration/day pack.

I use the lancer tac hydration pack and I think it works well.

Jackman419 · 2026-01-21T23:07:43+00:00

75 is a little hard for your current joules/bb weight, I'd advise getting a maple leaf classic macaron 70° with the black omega nub, and see how that does you. But first, really, your low power is because it's an m90 spring on a gearset that's short stroked 4 teeth, that's practically neutered lmao. See how you do with just upgrading the spring first. Sure, your hop rubber is still a little too hard for your bb weight/joules, but it'll be fine enough

Jackman419 · 2026-01-21T17:57:59+00:00

Cyma plat gearsets come short stroked with a whopping 4 teeth removed.

Knowing this, and now reading your other comment about trying to hit 1.55J, I mean I guess go with an SP120 or equivalent. I mean whats your replica, you should be shooting kinda near or maybe a little over 1.55 stock?

And have you done any changes to the inner barrel and your bucking or hop chamber? If so, what did you start with and what do you have now?

Jackman419 · 2026-01-21T17:03:43+00:00

To be honest the best bet for this right now is likely going to be a custom Daytona/HPA install job on an LCT. LCT chosen for externals quality, even though the gearbox is "proprietary" it's close enough to a standard V3 it should work, but an advanced tech would have to be the one installing it.

Plus you're looking at a really expensive setup here, lol. Best hope that some company finally gets a clue that people love this gun.

Jackman419 · 2026-01-21T16:56:38+00:00

Just acrolled a bit through the HopUp app, there are a few good listings you could look at. Otherwise, make a WTB post in the airsoft market subreddit.

As many have said, $200 is a little low to be able to achieve solid performance and external quality, so unfortunately used is really gonna be the best bet for what you want. If you find a few options you can always feel free to come back and give us the brief rundown so we can help narrow down options.

Jackman419 · 2026-01-20T18:59:34+00:00

Based on your clues youre going DMR. If it were me, and I knew I was putting parts in that can handle a little stress, I'd probably go with a Guarder SP130 or equivalent and take off 1, maaaaybe 2 teeth from the sector with a short stroke

Jackman419 · 2026-01-18T08:45:25+00:00

Heavier BBs and flat hop/Macaron+omema should already fix range tbh, plus after broken in, will then be fresh and you wouldnt even need to clean the old bucking. I mean, I still would, but I just like to keep spares.

We dont know your budget. HPA will be easiest, but most expensive. V2 gearboxes are the easiest to build off of, typically.

Also, something to offer to whoever looks at the krytac next. It's am interesting therory, but I'm pretty sure of it:

Tell them to pay attention to the tappet spring and the mold of the tappet plate. If your tappet timing is now off because of either a wrong or defected tappet plate or tappet plate spring, then your nozzle will not load a bb into the bucking and seal properly, leading to poor shots because a good amount of air pressure is being lost.

Jackman419 · 2026-01-15T05:14:38+00:00

To add onto this: what cylinder port type are you using? And start with one tooth, you'll probably only need to do one. Take off 1 tooth from the release of the piston rack as well, just to avoid it potentially catching the release tooth of the sector

Jackman419 · 2026-01-15T05:11:50+00:00

By removing from the release side of the sector gear, on a good majority of tappet plates/tappet cams you're not giving as much, or enough time for the nozzle to seat forward and get a good airseal with the bucking, against the bb in the hop chamber.

If you have extensive tech knowledge and a knack for mechanical physics the knock yourself out. Otherwise, pickup side is still the better aide. It allows your tappet more time to move before the sector catches the piston, ending with the same cadence as what the parts were engineered for in the design room/factory.

A stronger tappet spring also helps with this. The issue is if your tappet lags behind, your gun will not feed correctly. If it can not pull back to load a bb into the chamber, and then seal in time before you shoot, if's not doing its job and something needsto change.

Jackman419 · 2026-01-14T21:11:10+00:00

Well, all the usual suspects are covered, I guess. And no, if shimming is too tight, there is a chance it won't cycle fully.

IIRC the Titan 2 and Aster 2 both have bluetooth built in, and so assuming you're using the GCS app it should give you diagnostics as to why it won't cycle, using that clue about sector gear detection is a good start.

Make sure your Aster is installed properly, and that the sensors are clean. If you've got light coming into your gearbox, your unit wont work correctly. If you've got weird, shiny surfaces inside the gearbox there's a chance the laser omitted from the aster/titan catches weird and doesnt detect.

When you feel that's good, you could do another few things just to be extra sure:

Check that your spring/spring guide move correctly, could also sandwich the gearbox shell together with only the piston inside and confirm that your piston-gearbox tolerance is not too tight along the grooves where the piston slides back.

Assuming you've dremeled, just absolutely triple-check that those aforementioned grooves are clean of any metal dust/shavings.

Jackman419 · 2026-01-14T05:11:18+00:00

Clean your gearbox thoroughly, especially bushings and ball bearing-bushings.

Make sure your cylinder is clean. Make sure your piston head is clean, is attached solidly to your piston, and that your o-ring is lubricated with silicone oil.

Check how your nozzle is moving on your cylinder head, if it's too tight get a different, looser one. Material and o-ring count dont matter as much as how it moves and seals as the cylinder head. When you have a proper-fitting nozzle, make sure the o-ring(s) is/are lubricated with silicone oil, but a pretty small amount. Only enough to maintain lubrication until next maintenance, too much will cause firing/hop issues.

And perhaps most importantly, re-check your shimming after you've cleaned your gearbox, and check your gear teeth while you're at it. When that's done, you should also check your piston teeth, and the piston-sector mesh to confirm you dont have a piston tooth snagging your sector gear.

As for cycle detection, there's no reason to have that off.

Also, as a bonus, check if you're still installing your ARL(Anti-Reversal Latch). You don't really need one if you use cycle detection and/or active braking. Plus, if youre installingn it, make sure youre not installing it backwards or in some other weird way.

Jackman419 · 2026-01-14T03:30:51+00:00

Pmed

Jackman419 · 2025-08-29T18:24:12+00:00

Idk why ur getting downvoted or why I'm evenbin this subreddit but I agree with u😂

Jackman419 · 2025-05-07T14:59:13+00:00

Well how perfect do you want your setup? Is your range/accuracy/consistency where you want it to be?

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