Double Eagle M908A DMR "Build"

[Fatboy40]

I bit the bullet yesterday, an e-mail from BBGUNS4LESS offering me 5% off of my unplaced order / basket triggered it, and a Double Eagle M908A is now on the way to be setup as a DMR. In the UK right now there are only two retailers left with it in stock, BBGUNS4LESS and High Pressure Airsoft, which is a little frustrating considering that TaiwanGun has the entire M90X range in stock.

I'm not a speedyboi, and enjoy hanging back a bit and playing support, so I've wanted something to use as a DMR for quite a few months and the M908A fits the bill for me. A few things that swung it for me are the longer battery cable (I use a GATE deans extension cable in my M904E), a metal receiver with only one selector so I can drill and tap a hole in it to screw in a bolt for mechanically locking it to semi-only (not everywhere will allow a DMR's MOSFET just to be set to single shot on all modes), quick change spring, the rip off GATE Titan so that in the future I know for certain I could swap in a genuine Titan easily if I wanted to, and I've taken apart my M904E's gearbox multiple times now so I'm happy to do this and the M908A's will be identical.

I won't initially be doing anything major to it, but may have to if the stock piston gets chewed up (the stock rack is part metal teeth with the rest plastic, we'll see what happens), and will stick with the stock 385mm inner barrel but will swap in a Maple Leaf Macaron 70 degree + omega nub + Gearparts M120 spring (with an M130 bought as well just in-case). The stock DE piston head and spring guide both have bearings, so I'm thinking this will compress the M120 spring more than usual and get me close to my primary sites 420 FPS DMR limit.

I'm going to start with 0.30g BBs, so that's why I'm using the 70 degree bucking and omega nub, and this should hop them happily.

My only concerns are that my eyesight isn't what it used to be, so I'll play one game with it and may invest in a flip-to-side magnifier (nothing too cheap, but still a clone) if I do get good range, and also that the stock motor may not have enough torque to do the job (and if not it's then do I go with a brushed high-torque or a Warhead Base motor).

 

[RostokMcSpoons]

Good luck with your build, will be chomping my popcorn on the side-lines, watching with great interest!

As my CA M15A3 shoots best on semi-auto and has a stupidly long barrel, I might go the DMR route too, though it won't be easy as the DE with the lovely quick change spring system.  

I've fancied the idea of one of the magnifiers too... but from what I've read you have to be careful to find one that has a decent hinge so it stays up / down as required.
So I thought a low power zoom scope might be a safer bet.

 

[Fatboy40]

I got to play with my new DE M908A this weekend, another good Sunday out where we all enjoyed ourselves (myself, my son, and a friend of his). My experience with the tweaked M908A though was a bit 50/50, and I'm not sure how long this post will be so I'll probably follow it up with another in a day or two with a few photos.

Out of the box the rifle was pretty gutless, only 315 FPS on 0.20g BBs with no hop on and 11.1v Titan LiIo battery, so even to use it as an AEG it would have needed a spring change.

First of it was swapping in a Maple Leaf Macaron 70 Degree and Omega Nub. Like my son's M906C the arm of the hop unit had an extra recess to hold the red rubber nub in it, with the nub having a bump on its top that fits in this. Now, this is nothing scientific, but this arm is not the same as that on my earlier M904E which is a traditional arm as it appears that the arm with the recess even with no hop actually applied is pushing down already and introducing hop. Even a slight turn of the hop units wheel pushed the nub down heavily, and even with no hop set at all the FPS was down to 288. Also, and this may be more down to the inner barrel and its manufacturing / quality or the same of the hop unit, but the substantial "patch" of the ML bucking just would not maintain a inform shape with or without hop applied. 

Next the spring, and in went a Gearparts M130 spring which gave me 433 FPS on 0.20g with no hop, and 412 FPS on 0.20g with a small amount of hop. All good for the site I primarily play at which has a 420 FPS DMR limit. So far, with my chrono and some back garden action all was looking good, and a cheap Eotech XPS2 red dot and G33 clone magnifier finished things off so I was ready to have a real game with it using 0.30g BBs.

Onto the skirmish with it and arriving nice and early it was a jaunt out of the safe zone to set things up, and the results were somewhat disappointing. The range was there, I could shoot out to 60 meters or more fine without having to lob the BBs at all, but the hop was all over the shop and miniscule adjustments produced wild result sending BBs into orbit after 40 or so meters or occasionally almost no hop at all. The actual games showed that the range was there, however now it was obvious that grouping at distance was crap, at times it felt like the BB's were maybe up to 1 1/2 feet either side of center out at 40 to 50 meters so I had to fire five or so shots to get a hit and my DMR became a long range support gun to be effective.

As I said above it was a good day out, and we all had fun, but the M908A obviously needed a lot more work to it with my wallet being hit again. So, we're now onto me buying the following... a ZCI rotary hop unit (I don't trust the stock one, and don't need the smoke and mirrors of an overpriced bright yellow metal unit if you know what I mean) + a Maple Leaf 410mm 6.02 inner barrel (longer than the stock 385mm one) + a Maple Leaf MR 70 Degree bucking (I want accuracy at range) + a Gearparts M110 spring (I've still got a spare M120 but I want options just in-case the ML inner barrel makes things hotter than expected). At the moment I don't think I need to play around with cylinders.

On a positive though I think the M908A as a platform is spot on, it has the great optical controller, the knock off Geissele handguard is nice, the outer barrel is long enough to support the size of inner barrels I'll need, and the metal receiver was easy to drill and tap an M4 hole so I could mechanically lock the rifle to semi-only.

I think my next game may be on the 16th February, so more than enough time to do some more work on the rifle.

 

[RostokMcSpoons]

I'll have to order up some more popcorn with all those extra upgrades going in...

 

[Ebeneezer Goode]

Interested to see the comment regarding "only" 315fps. That's slap bang in the middle of a normal AEG performance and IMO perfectly reasonable, I wouldn't say "gutless".

Careful not to make the mistake of trying to maximise FPS on .2s only. Personally I'd tune the gun to whatever weight of ammo you are using rather than just on .2s as otherwise results can be erratic. Use a joule graph and work out your target from that... although I'd concentrate more on achieving a consistent hop, as that's what will get you your range and consistent accuracy, rather than chasing fps limits.

 

[Cr0-Magnon]

I've just had these two DMR's built by Negative Airsoft. There really is a hell of a lot more involved than just changing the barrel, hop and spring. If you're a decent enough tinkerer, then you'll likely have some fun learning a long the way. I'm obviously not, which is why I just put my hand in my pocket from the start.

View attachment 83961

 

[strykerles]

I've just had these two DMR's built by Negative Airsoft. There really is a hell of a lot more involved than just changing the barrel, hop and spring. If you're a decent enough tinkerer, then you'll likely have some fun learning a long the way. I'm obviously not, which is why I just put my hand in my pocket from the start.

View attachment 83961

nice looking guns

As for tinkering I love trying it, it's great when you put it all together and it just works

Built a DMR from a Cyma VSS and it now sends .43s straight and true for a long distance

View attachment 83969

 

[Cr0-Magnon]

nice looking guns

As for tinkering I love trying it, it's great when you put it all together and it just works

Built a DMR from a Cyma VSS and it now sends .43s straight and true for a long distance

View attachment 83969

I'm envious of those who can do it themselves. Must be very rewarding.

 

[RostokMcSpoons]

I'm early in my tech'ing journey. 

First attempt was a bit of a disaster, but I've tried again.  And after quite a few painful hours I've learned a lot.
I might not be doing it right yet (time and a few thousand BBs will tell), but it's interesting and fun, and gives me something to obsess over that's cheaper than looking for and buying whole new guns

I recommend you pick your least-used gun and give it a go!

 

[strykerles]

I recommend you pick your least-used gun and give it a go!

I brought the Cyma brand new and gutted it straight away as I got it to DMR it ?

First spring I put in should have given it around the 440fps mark with a .20

clocked in at a highly illegal 562fps ?

 

[Fatboy40]

A quick turn around from AK2M4 allowed me to replace a few other items today in search of better control of hop and grouping, so in goes the Maple Leaf 410mm AEG inner barrel and MR HOP 70 degree bucking, along with an AK2M4 hard Omega Nub all in a ZCI plastic rotary hop unit.

As it should do the MR HOP sat perfectly in the cut-out of the inner barrel, and when all assembled the patch sat so much better than the Macaron in the stock DE inner barrel and hop unit. Staring down the hop unit the patch, very concave before fitment, looked a little flatter with some hop applied so a little bit flat hop / a little bit R hop looking. I'm itching to get somewhere with enough range at the weekend, not an actual game though, to see the results.

The FPS with no hop applied has gone from around 438 down to 418, with the new inner barrel being 25mm longer, which is more of a drop than I expected going to a slightly tighter bore. I need to play a proper game to see if this has any negative effect at all, however I've a 4/5 cylinder to replace the stock 3/4 if need be (as far as I'm aware all DE M900's have 3/4 cylinders, all internals are identical across models, so for a model like the M906A that has a 420mm inner barrel this can't be good for air volume?).

@Cr0-Magnon if you don't mind me asking what did Negative Airsoft do to your M4 / AR15 for you / what parts did he replace?

 

[Cr0-Magnon]

I could go back through the videos he sent and list them but really I believe teching is less about replacing parts for more expensive ones and more about knowing which areas to address when a gun isn't performing the way you want. He spends so much time modifying existing parts and fine tuning, that really most of the expense ends up being labour. As I'm sure he'd also say, while there are tried and tested quality parts, what works in a gun varies massively, not only between make and model but even two examples of the same!

Saying that, I do have a warhead motor in the G&G M4 and that thing is phenomenal. Instant trigger reaction and doesn't seem to get hot in the same way a normal Airsoft motor does. Again though, it went straight in to my gun. For others, extensive modification could be required to get it working perfectly. That's where experience comes in and exactly the kind of thing I'm happy to pay for.

 

[Fatboy40]

I picked up a battery from my local sites shop early on Saturday morning and was allowed to nip out onto the site for a few minutes to test the changes. So with the Maple Leaf 410mm AEG inner barrel, MR HOP 70 degree bucking, AK2M4 hard Omega Nub all in a ZCI plastic rotary hop unit grouping at a distance was much better with no veering to the left or right (the ZCI hop unit is admittedly not "high end", but it's of a noticeably higher quality than the stock DE one, especially the fitment of the arm). I know for certain now that I'll be more accurate at a good pinch point where I can be useful to team mates out to around 52 meters.

However, beyond 50 or so meters results get a bit disappointing in that the hop doesn't seem to be consistent enough, however I genuinely think that my setup hop wise is about the best I can do as I'm using sound components carefully assembled. I'm wondering if I should be considering the weight of the BBs I'm using?

I've started with 0.30g BBs, where I normally use 0.25g for my standard AEG, as I was wary of starting off at very heavy weights and also considering my favourite site has a 420 FPS DMR limit. I'm not really sure what weight I should have a try with, in that 0.32's are only a tiny bit more expensive but will they make any noticeable difference, and once onto 0.36 or 0.40 prices leap up a hell of a lot.

 

[RostokMcSpoons]

You're going to be a pinging aimed shots in semi-auto, your ammo usage will be so low compared to a normal day's spamming of 3-5 round bursts.  It's got to be worth trying 0.36's
And the cost of the BBs compared to your outlay (and whatever monetary value you could attach to 'disappointment') mean it's a price worth paying anyway

 

[parallel-knight]

YO can some one please help me! I'm gonna be putting together a DMR/Recon set up and my DMR is gonna be The CYMA VSS. I'm really struggling to find out is the PSO-1 scope will fit the CYMA VSS. there's some people that say it does and others that don't. can some one let me know if the CYMA VSS can actually take the PSO-1 scope? also if they know if it can take the standard AK mounts for optics. Although the only optic i want on my VSS is the PSO-1. withgout the PSO-1 my set up will never be complete. Please HELP. 

My E-Mail : [email protected]

 

[strykerles]

@parallel-knight I have a pso and it does not fit. The bulb holder hits the dust cover. I will take some pictures later to demonstrate 

The cyma and lct models are not to scale so it won't fit. Afaik the only one that is correct is the NPO version and that is expensive 

LCT did do a riser for the side mount that would make it possible I believe to fit a scope although don't hold.me to that. Also they are rare now.  

You can buy side mounts that will fit and use a standard picatinny rail mounts. You can also buy pso scopes with a picatinny attachment method.

Msg me if you need to know anything else as I recently did the dmr mod to a vss

 

[Fatboy40]

I've still a niggling feeling that the air volume is too low so I thought I'd take steps to correct that before I next play. In the image below is the stock DE M900 cylinder at the top, it has to a 3/4, and the new ZCI stainless steel 4/5 at the bottom...

(full size image https://imgur.com/dCVy0jZ.jpg)

... and I'm keeping my fingers crossed this may be one of the final pieces of the puzzle (also it baffles me that the internals of all DE M900's are the same, when the M906A and 7A have a 420mm inner barrel so their air volume ratio must be very low, and with some of the poor quality springs going in them they'll be pretty gutless).

Also this is how the gun's looking at the moment...

(full size image https://imgur.com/z0AVJpA.jpg)

... and I just need to decide on what grip I want on the bottom of the handguard.

 

[RostokMcSpoons]

I had a good game today with my DE M906C.  As its quite a short barrel I'm guessing that the standard cylinder would be a fair match for it.  

I certainly didn't feel out-ranged and got some good long range kills of my own (but I'm guessing around the 40-45m distance, which I consider good, but when you're DMRing, probably not so much!)

That's with just the upgraded spring, hop and bucking.

 

[Fatboy40]

Playing just before Xmas 2023 my DMR shat itself, only a few minutes into the first game, a grinding noise and then no nozzle movement. I assumed that I'd stripped a gear, but had to wait until Jan 2024 to take a look as I didn't buy any parts before AK2M4 closed for the holidays.

Taking it apart today it was totally not what I expected, in that the screw holding the Maxx Model piston head onto the XT full metal rack piston had worked loose and somehow jammed the piston in its rear most position (and the M130 spring had a few kinks in it). I had used Loctite, but it was a bit on the old side and a quick Google says that it does have a shelf life so my bad

Everything else was good though so got a new XT piston from my spare parts box, along with an XT piston head with bearing and fitted them. I also decided to swap to SHS 18:1 gears and go from a 4/5ths cylinder to a closed / full one so moved down to a new XT M120 spring to first test with. All is good, however with the full cylinder and M120 I'm now just a fraction of a Joule off of the DMR limit for my local site so I'm well chuffed with that

Secretly I'm hoping that the full cylinder will equal an extra foot or two of range, so can't wait to play again.

 

[Lord_Mandrake]

Any chance you could list the upgrades you've made to your 908? I'm a new player looking at a DE 9XX as my first AEG, and plan to upgrade it to a DMR (max. 420 fps at my local site) in the near future. Any tips gratefully appreciated.