Double Eagle M906C - Internal upgrades / tinkering

[RostokMcSpoons]

19 minutes ago, Adolf Hamster said:

in fairness, i am starting to wonder if you're getting near to that being the limiting factor. as with all things it depends on how far you want to go in terms of when you think good enough is good enough.

 

I think now I've got a consistent muzzle velocity that's holding the same day-to-day, it has now reached "good enough".  But I was a bit taken aback when someone else mentioned getting 65m hits with their DE.  To be fair I've got no idea what my gun will shoot to now, I'm limited to 18-20m max at home, so I'll not fret too much until I've got out to the site again. but that seems unlikely for mine if I'm already grouping at 3-4" at only 15m.

 

Most of my focus is back on the F2000...

I've also got my AK47 which is currently dead due to a blown fuse, and needing the nozzle replaced - so another v3 gearbox opening.  Ho hum.
And my CA M15 is still shooting off to the right again, and also down at 270fps so that needs a spring change.  And I might change the front end for a VN M16 handguard... cos they're cool.  

 

So plenty to muck about with still!

Edited December 29, 2021 by RostokMcSpoons

[Adolf Hamster]

15 minutes ago, RostokMcSpoons said:

But I was a bit taken aback when someone else mentioned getting 65m hits with their DE.

 

always take claims of airsoft range with a big heap of salt, for starters airsoft meters are well known to be a different length to metric meters, and many folks will have different versions of what they mean by getting hits, dumping half a magazine into space for one round to barely be noticed, or firing one shot straight and level and hitting every time, wether it's a full target or someone hiding in cover etc.

 

21 minutes ago, RostokMcSpoons said:

but that seems unlikely for mine if I'm already grouping at 3-4" at only 15m.

 

eh, can be tricky to tell. i've never done any proper range testing always went with just how it felt in the field.

[RostokMcSpoons]

Well... damn it.

The gun I never wanted to crack open and meddle with, needs cracking open and meddling with.

 

I tried to do the quick change spring thing, to see if a new M105 would lift my fps back to the 345 fps I chrono'd at recently, and that simple job went a bit awry.  As I pushed the spring guide in, it felt like the spring popped downwards and the spring guide went deeper into the gun than I expected.  I took it back out and cycled the gun without a spring, and it works... but it's now got the piston all the way to the back.   I think I've managed to get things out-of-sync (but I'll take advice on that).  With the piston backwards it's going to be hellish to force the spring in, but it feels like a bad idea anyway...?

(Edit: I realised I could manipulate the bevel gear, and that got the piston forward.  I re-installed the spring, but the gearbox clicked and the fire control unit beeped back at me when I tried to fire.  So yeah, something is officially askew on treddle.   The motor still runs when out of the pistol grip, so I've not killed that or the mosfet)

 

So I'm now at the point where I'm taking my beloved rifle apart, not really being able to remember how M4 / V2 gearboxes are disassembled.  I can't get the gearbox out of the lower receiver, though I've taken off the pistol grip, the selector switches, popped out both big body pins, and also the thin pin above the trigger.

The remaining thing retaining it in place now seems to be magazine catch bar that runs across the body, and through a hole in the gearbox.   I'm not entirely sure how to remove it.  Any hints?  I can only find YT videos of the 904 and that seems to be built a little differently - there's a removable screw in the mag catch on the right side of the receiver that doesn't seem to exist on mine.
 

 

 

Any thoughts, as always, hugely appreciated

Edited February 28, 2023 by RostokMcSpoons

[Adolf Hamster]

that type of mag catch looks to be the type that the bar is threaded into the button, so you gotta push the button all the way in then unscrew the other side.

 

they're a bit of a pain as often the bolt catch paddle needs to be removed to give clearance.

 

 

as for the spring, sounds like initially it got kinked and dropped downwards, not really a big deal unless it gets stuck or bent permanently, just pull it out and reinstall.

 

for the piston in the rear position, the lazy way to solve that without cracking the gearbox is to use a flat ended tool (a punch or a flat ground hex driver, basically anything that won't scratch the piston head more than you're happy with) up through the nozzle to push the piston all the way back then it'll usually be able slide forward again. you don't have to pull the motor, but doing so will reduce the force required to push the piston back.

 

at the risk of creating a "do'h" moment the clicking after reinstalling the motor, sounds very much like the polarity of the motor is reversed, so it's running backwards into the arl before the mosfet kicks in and starts complaining.

 

[RostokMcSpoons]

Thanks!   The mag catch was just as described.  I was trying to take the bolt catch paddle off, but still can't figure that out.  Anyway, with a bit of persuasion the mag catch bar did let me unscrew it over the top of the paddle.
So now the gearbox is retained just by the bolt catch ambi connection.   :Sigh: 

 

I did take care about ensuring the motor was the right way around and attached to the leads correctly... but hell, I could still have done it wrongly.

What worries me now is that the piston is able to move backwards and forwards freely inside the cylinder... there's nothing engaging with the gear   Has the rack perhaps stripped out from the piston?   I can't hear anything rattling around, nothing seems broken as such

[Adolf Hamster]

Just now, RostokMcSpoons said:

Thanks!   The mag catch was just as described.  I was trying to take the bolt catch paddle off, but still can't figure that out.  Anyway, with a bit of persuasion the mag catch bar did let me unscrew it over the top of the paddle.
So now the gearbox is retained just by the bolt catch ambi connection.   :Sigh: 

 

that's the joys of the m4 platform for you......

 

2 minutes ago, RostokMcSpoons said:

I did take care about ensuring the motor was the right way around and attached to the leads correctly... but hell, I could still have done it wrongly.

 

honestly motor wires are like usb sticks or unlabelled push/pull doors, despite there being only 2 ways to do it they unfailingly require 3 attempts to get right

 

4 minutes ago, RostokMcSpoons said:

What worries me now is that the piston is able to move backwards and forwards freely inside the cylinder... there's nothing engaging with the gear   Has the rack perhaps stripped out from the piston?   I can't hear anything rattling around, nothing seems broken as such

 

is it not just the sector still sitting in the "firing" point of it's cycle? or are you turning the gears over and it's not moving the piston?

[RostokMcSpoons]

I'm trying to turn the gears, but now I've looked again, it seems it's springing back and I've not really been turning anything.  So yeah, quite possibly still in firing position.  I presume it's either the ARL or tappet plate spring providing the resistance? 

 

Worth just putting it back together and trying again?

 

Awww damnit, I'll give it a go

 

... bet ya I had the motor in back to front ;]

 

 

 

 

Edited February 28, 2023 by RostokMcSpoons

[Adolf Hamster]

26 minutes ago, RostokMcSpoons said:

I'm trying to turn the gears, but now I've looked again, it seems it's springing back and I've not really been turning anything.  So yeah, quite possibly still in firing position.  I presume it's either the ARL or tappet plate spring providing the resistance? 

 

depending on where it is tappet plate would be the most likely culprit

 

28 minutes ago, RostokMcSpoons said:

... bet ya I had the motor in back to front ;]

 

just act casual and hope nobody noticed, that's what i always do

[RostokMcSpoons]

It's alive, but I have buggered it a bit. 
I lost the tiny spring from the selector lever.   I've still got the tiny ball bearing, but the spring (which was along side) must have got attracted to something magnetised (like one of my allen keys), or caught a gust of air and gone walkies.  It's too small to find, I just hope it's not inside the gun ;/

Maybe as a result of the lever being able to move too easily, or because I didn't align the selector somehow, it's now sometimes beeping rather than shooting.  

To add insult to injury, it's chrono-ing at much the same velocity as it was before I started all this palaver - there was nothing wrong with the spring.

@ak2m4  do you have the detente springs in stock - or know what size I need to get off eBay / Amazon?

Edited February 28, 2023 by RostokMcSpoons

[Adolf Hamster]

1 minute ago, RostokMcSpoons said:

I lost the tiny spring from the selector lever.   I've still got the tiny ball bearing, but the spring (which was along side) must have got attracted to something magnetised (like one of my allen keys), or caught a gust of air and gone walkies.  It's too small to find, I just hope it's not inside the gun ;/

 

oh dear, it's definately migrated it's way to outer mongolia by now.......

[RostokMcSpoons]

Hahaha the problem with it not shooting... I have a Deans extension cable on the gun, to make connecting the battery easier.  To 'make sure' it doesn't get disconnected, the connectors are wrapped in electrical tape... which had hidden the fact it was very nearly disconnected!

Without the stock, the battery was occasionally dangling from the gun... it had pulled apart to the point there was just a tenuous connection - when I moved it, it would either make or break, setting off the (connection) beeps.

 

I am SO relieved I haven't broken my lovely gun.   Now I just need to get a decent fix for the selector lever.... 

[ak2m4]

@RostokMcSpoons I don't really,  I have some longer ones which seem the right OD but from experience I've noticed brands use all sorts of different sizes.  Maybe someone can measure one?

[RostokMcSpoons]

13 minutes ago, ak2m4 said:

@RostokMcSpoons I don't really,  I have some longer ones which seem the right OD but from experience I've noticed brands use all sorts of different sizes.  Maybe someone can measure one?

The ball bearing is 2.4mm diameter, so, bearing* that in mind and from my (goldfish) memory, I'm going to say ~2mm diameter, 3-4mm long would seem right, it was a tiny spring.

Edit: Pics on my new Fire selector thread
I could buy the mixed pack from this eBay page and cut one down to size...?

 

* Pun not intended, I wish it had been 

Edited March 1, 2023 by RostokMcSpoons

[ak2m4]

26 minutes ago, RostokMcSpoons said:

The ball bearing is 2.4mm diameter, so, bearing* that in mind and from my (goldfish) memory, I'm going to say ~2mm diameter, 3-4mm long would seem right, it was a tiny spring.

Edit: Pics on my new Fire selector thread
I could buy the mixed pack from this eBay page and cut one down to size...?

 

* Pun not intended, I wish it had been 

 
let me have a quick look this afternoon and I'll send you some over, I'm sure I'm got loads which will fit 🙂

[RostokMcSpoons]

I watched a short video about fitting replacement selecter levers, where the guy complained about the fact the spring and ball are often not supplied.  He suggested using a Cutoff Lever spring, cut down to the right length.  So that might be a better guide than my bad memory for what the original looked like

[ak2m4]

@RostokMcSpoons found one, it's OD is 2.4mm, I'll message you direct

[RostokMcSpoons]

My DE still isn't quite behaving itself, but in a somewhat unexpected way.

 

I have successfully chrono'd my gun at 305fps with 0.28g BBs.  Which is peachy, that's actually a little hot (should be 296), but the bit of hop required for accurate long-range shooting brings it nicely down to that.  Or should do... if I could do that.   Because that chrono result is currently only achievable when I have no hop nub / arm in place!
With the arm + Omega nub in place, I can't dial out the hop altogether,  in fact it's over-hopping the 0.28s at 15m... and consequently the hefty amount of friction was bringing it down to ~245fps.

This is what it was looking at with allegedly zero hop...

 

So how can this be?  I've checked the nub is correctly located in the arm, both when fitting and when removing it again (The second attempt I used a smidge of Blu-tack to keep it in place, just to make sure it wasn't moving into a weird position)

I tried changing back to the DE's original (figure of eight, squishy) nub.   A bit less impingement but still there.

Ok, maybe it's the G&G Green hop rubber.... so I swapped out for an ML Macaron 50deg.   
A bit less but still there... I'm up to 275fps but it's still slightly over-hopping at the minimum setting!

There aren't many parts to this equation, what on earth could I be doing wrong?

Or do hop rubbers become less intrusive as they wear-in?   (I'm sort-of tempted to go rooting around in my bin for the old knackered one!)

 

Edited March 2, 2023 by RostokMcSpoons

[Adolf Hamster]

the omega nub isn't designed to be used with anything but the maple leaf rubbers, so i wouldn't be surprised seeing those symptoms with a standard style bucking.

 

that said, it shouldn't really be doing that with the maple leaf bucking.

 

these are a rotary style hop aren't they, is it possible the tail end isn't engaging in the wheel in it's correct slot?

 

also worth looking down the barrel whilst moving the hop through it's range of motion, see if it's actually moving as it should.

[RostokMcSpoons]

I'm looking down the barrel to check it... the rotary wheel has a slot that only runs halfway around, it's definitely correctly engaged, and the hop applies just as expected - it's just the starting amount that's wrong.
it's weird it's like this now and affecting the velocity so much, whereas everything was fine up to my previous skirmish.

[Adolf Hamster]

In that case it does really sound like the nub has ended up in an odd position/orientation, but you've already checked for that.....

[RostokMcSpoons]

I found the old ML Macaron 50deg hop rubber (tatty and grubby as it is), re-installed it, fps back up to 290fps) at minimum hop with 0.28's.
Looking down the barrel there's still a little bit of impingement at the lowest setting, but it's the least of the three I've tried, and that's with the Omega nub in place.
I'll test it outdoors later, it's a little early to sling BBs now, but I don't expect this setup to over-hop.   Back where I was 4 weeks ago?  Maybe.  The feed lip is slightly shredded, I think it might be adding it's own spin to the BB to spoil my accuracy... except it's been bettter than 'fine' in the last skirmish.

 

Airsoft... it's as much art / luck as science...

 

Edited March 3, 2023 by RostokMcSpoons

[RostokMcSpoons]

Luke at Negative Airsoft has just published an upgrade video of an M906C

 

He gives it big love

 

 

I think mine has definitely started to run at a lower RoF than it used to, really time to get a replacement motor in, and by the contents of this video I should crack open the gearbox to check the o-ring and piston etc are all ok

 

 

I'll need some Brave Pills, nurse

[Colin Allen]

36 minutes ago, RostokMcSpoons said:

Luke at Negative Airsoft has just published an upgrade video of an M906C

 

He gives it big love

 

 

I think mine has definitely started to run at a lower RoF than it used to, really time to get a replacement motor in, and by the contents of this video I should crack open the gearbox to check the o-ring and piston etc are all ok

 

 

I'll need some Brave Pills, nurse

If the power is ok and it sounds reasonable, why open it up?

[Leo Greer]

There’s a decent chance that your DE will never be the same again if you open it up. Airsoft gnus have strange and inexplicable magic that comes into play, making each and every time you open it create new variables. 😂

[RostokMcSpoons]

Yeah I've resisted the temptation to do it before, but the guns rate of fire has dropped recently (not by much, but enough to show up when testing using my chrono)... I'll swap the motor first