Jump to content
Sign in to follow this  

M4 to DMR

Recommended Posts

Hi guys, I'm fairly new to the gun upgrading scene and I'd like to know if all M4 platforms are compatible with each other (interalswise)

I'm familiar with the internals on an AEG M4 but not too familiar. I have a cheap Cyma and I'd like to upgrade it to an DMR but I don't know if it is just purchasing top of the line internals and they all fit perfectly or if they have compatibility problems and I have to be very carefull with what I buy.


Edit: This is my current gun: https://www.taiwangun.com/en/electric/cm-515-cyma?from=listing&campaign-id=19

I'm considering selling it as it doesn't have a quick spring change mecanism wich would be very helpfull because of the different fields I play in, and if it would be advantageous to switch to a more upgradeable M4 platform (if there is such a thing)

Share this post

Link to post
Share on other sites

Might help if you list actual model...

as Cyma V2's are a tiny bit bespoke


Spring guide is a V3 not a V2

Trigger switch, requires the copper plate on selector plate to make contact with prongs at back of switch

(pretty sure this is quite common on Cyma V2's), not something to worry about unless you break selector

(or mod/use another selector plate to lock to semi only), if using a mosfet then flatten & bridge prongs)


a v3 box but shows the mod if gun plays up firing due to contacts not touching copper plate...


Closer look at selector plate and microswitch | Bingo Airsoftworks


or another way, though thinly soldered is for say a mosfet, use thicker join to bridge if no mosfet

I flipping hate AEGs - Electric Guns - Airsoft Forums UK


how it usually is and the plate prong issue that can "sometimes" occur on "some" switch/selectors


www.horsefish.net - /airsoft/images/safe-semi-semi-selector-plate-mod/


Then remove material to prevent Cut Off Lever rising to allow full auto...


how to disable fully auto on a we tech m16/m4 | Airsoft Society ...


Now the gun is locked to semi only on DMR's with selector mod

The prongs was just being pointed if you use a spare selector plate without copper plate

(or ran into issues that it doesn't fire 101% of time due to poor contact of copper plate/prongs)

There is a couple of other mods or replace switch, but flatten contacts & bridge is very quick if using mosfet


These days the "prong" switches have started to be used less & less, but some people still fit them

and they often work OK, but can cause issues if they fail to make perfect contact in both semi & auto

now & then in say semi, plate halfway across its travel there "might" be issues with sporadic firing, but fine in auto


Cyma V2 tappet plate is also a little bespoke or deviates from most regular aftermarket ones like SHS

The Cyma tappet has cut-outs upfront where the front is reinforced slightly on the inside...



compared to SHS V2 tappet...



but can be modded...


loss of power - Electric Guns - Airsoft Forums UK


Reason why tappet is mentioned coz the SHS Red nozzle sits very loosely on clear Cyma tappet

But black SHS plastic nozzle with slot sits better on Cyma tappet...




So you have some options regarding the few minor qwirks on Cyma V2's


Box is reinforced at rear, so higher speed gears like 13:1's need a bit of modding to top of case

but if you are looking at DMR you probably stay with 18:1 or maybe 16:1's which will fit OK


The std motor in most cheap Cyma's is a 27/28tpa which has some torque but rather slow

So would need to look to running on 11.1v on stock motor to add some zest

or replace motor with a stronger neodym motor and run on 7.4v or 11.1v depending on speed/spec

(Basically you want something that cycles at say 12rps on 7.4v then use 11.1v to fire at 19rps say)


There are numerous options, more than one way to skin a cat etc...

But do you REALLY want a DMR ???

Miss out on most the action just taking pot shots on semi ???


Clean up barrel, set hop well or replace with say Maple Leaf Macron or something

use decent .25's and stick with a reg AEG with better accuracy

maybe chuck on a pair of deans over tamiya


and just use it as it is, more fun, less grief/hassle

if/when it plays up then look at some replacement bits and some tweaks

But I wouldn't go nutz on it, it will STILL be a cheap Cyma no matter what

(a pretty good cheapo gun, but I would go too nutz chucking "top of the line internals" in there myself)


If you got a CM515 or CM518 then get it running sweet & a bit more accurately @ 340~348 fps, job done

add a bit more zest/juice/motor at some point perhaps but still think I'd use it as AEG than DMR

But up to you, just a small heads up on some of the minor qwirks on Cyma V2's as requested


Share this post

Link to post
Share on other sites

Not bad guess on the 515, said 515 or 518 as they are the popular cheapo's

(the 517 is a nice cheap Raider for those on really tight budget)


From TWG - probably CM621 but has a bespoke Mosfet- ol' Jefftron type with whistles

Still basically a tarted up CM515, lots of plastic like the plastic sights and some fake ambi select stuff

So not a Specna Arms beater at all - but cheap-ish


Still £50 more than your 515, QC spring & mosfet, plus has the not so reinforced box so 13:1's can drop in

but still bespoke tappet plate like v2 Cyma's use - no real biggy


The mosfet, if/when it fails you will have a job getting replacement I reckon, but then again G&G ETU's aren't perfect either

(often people rip faulty ones out & start again)


As said - not a Specna Arms beater from Gunfire, but GF charge more for postage AND friggin' paypal surcharge crap




I'd probably keep the 515 for field stuff and grab a cheapy titchy M4 for CQB

a metal FireHawk with stubby stock - friggin' made for CQB...




Now both might need some work, not the best hop units in either, plus almost certainly not QC spring

(plus GF shaft you more for shipping & paypal charges)

But if the AY is like certain ACM or Asia Guns guns, it will have a crappy hop & the black might come off

But that would make a nice CQB M4 base gun all the same, I keep eyeing one up myself


Or a SA mofo but be more money for a plastic/polymer CORE or more still for a metal EDGE M4 say


Thing is you ask these questions and you'll get numerous answers

The 621 is a cheap option with QC you seek, but really a tarted up 515

The £50 extra or so would be halfway to buying the stubby M4, so being more techy minded I'd lean that way

Others will say just buy a decent Specna Arms - so you already have 3 different answers depending on budget/tech ability


So there is no real perfect answer, though the 621 is perhaps a reasonable answer to your question






but as said it is just a QC tarted up 515, well not quite as long, about 330mm barrel compared to say 400

but can change spring in situ, early SA guns had a QC box but still had to remove grip/motor/box to change spring

So can as you requested, easily change spring over quickly if needed no problem

Share this post

Link to post
Share on other sites

My tech level is still fairly low, I've only recently started 'studying' how to upgrade my gun the the direction I want, wich is stealth and range (DMR, not sniper).

The quick change spring system is so that I can play as an assault M4 in the fields that don't allow for high powered guns. It really is very important to me having that, I do 30% of my games on a field with those limitations (1.3J)


I will try to sell my 515 and buy the 621 as you recomended.


A bit more specific questions about internal upgrades to the M4 platform:

Is this hopup chamber compatible with the above mentioned M4: https://combatevirtual.biz/pt/camara-de-hop-up/12876-maxx-model-me-sport-cnc-hop-up-unit-for-m4-aeg-2060000003621.html

And what about all other M4? Are they compatible with this as well?

Same question for this inner barrel: https://www.taiwangun.com/en/precision-inner-barrels/410mm-6-02-inner-barrel-for-aeg-maple-leaf?from=listing&campaign-id=14&q=mapple+leaf


This is so that I can understand how compatible the internals of an M4 are. Compared to snipers you have to very very carefull with the platform you chose, like you either go VSR or you have to dig the internet for the upgrades you want.

Share this post

Link to post
Share on other sites

According to the spec of 621...


Barrel is a 327mm (nice "floater" length) x 6.03 which qualifies as a tbb (so to speak)

Even Cyma cheapo std barrels are not that bad, with a nice crown so not a hacked up bit of pipe

(like some really shite cheapo plinkers have in them)


So the barrel shouldn't be that bad, nowt a bit of cleaning with rod will sort out with soft dry tissue


Most of the shot performance will down to bucking and decent BB's, which you should use if barrel is 6.03


Hence a Maple Macron yellow 60 & nub should improve things if needed


The hop - well hops can throw more stuff into the mix,

When changing bucking you can get lips pinched or protruding causing feed issues

& changing hops units can also throw up issues eg: ProWin often causes more grief than success


Personally I'd give it a clean up on the barrel and spend some time with decent 0.25's or maybe 0.28 bb's by say G&G

(honestly, cheapo BB's might feed ok(ish) in wider std barrels but on tighter bores, the slightest bit of egg shape or seam on a BB can give issues just feeding & clearing the barrel properly - forget if it goes straight or astray, cheap poor BB's really should not be used in tighter barrels

The amount of people that try this mofo barrel, hop, bucking setup say £60+ but still use shit BB's and wonder why results are not so great)


If you decide to play with shit, then get a half decent ZCI, SHS cheapy plastic or bit more expensive alloy rotary M4 hop

Maple blah blah blah, then build it as one unit leaving your std Cyma barrel/hop alone....


Chances are you may run into some issues getting the new barrel/hop combo sorted

or possibly tear bucking during the install - or whatever reason things don't go to plan....


If you run into issues on new combo, you still have the old barrel/hop combo to get you out playing, until you sort the other combo out


But for the moment, I'd see how it performs and tbh no two guns shoot the same out of the box

I've had one gun shoot quite good & a second one exact same model shoot shit

a torn bucking, installed a bit pissed or even had one instance where there was no nub - wtf ???


The really crap hop units I was referring to was clear plastic M4 hops, not so much the plastic but the quality of the unit

Most times the tension wouldn't hold the pressure/setting on nub/bucking and would loosen and lose its hop I dialed in

Normally you can add a washer/shim to add resistance and hold the setting, however the cheapo hard brittle clear plastic seemed to have almost stripped threads that would not allow me to tighten up even with washer/shim etc...

Plus there was friggin' grease all inside it - yeah on guns that had them clear traditional M4 hops, those cheapo clear hops were crap, found on very very cheap or poorly planned guns on a serious cost cutting mission - virtually useless


Cyma don't use these clear hops, but better quality black hops as the basic hop unit,

not brilliant but certainly not shit like some clear stock hops I've had in some guns in the past

Some people might have found them OK, but when I've come across cheap guns with clear hops they have been pretty shit and really needed replacing....




Cyma's aren't that bad, so I'd see how you go before you go nutz buying too many "upgrades", that if they don't work too well

or fitted slightly incorrectly, they effectively become DOWNGRADES instead

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Create New...