WE Gas Blow Back M4A1 Carbine

[Bamse]

If copper is more susceptible I doubt the cylinder is made of copper tho. an uneducated guess would be that #38 is copper in that case.

 

pure speculation; could there be benefits of cylinder shrinking the more cold it get so the seal becomes better?

[rvp69]

has any one used any new type of hop unit on the WE yet?

[danielsilva]

No part #36 is ok (I locktited it also). I use .30 bbs (Japanese made so they must be ok), I cleaned the hopup from too much silicon and locktited the valve with no result. Sometimes it doesn't fire from the first bb, it loads 2 bbs (and try always to rack, insert mag and release).

I don't know perhaps its the hopup. Have the new ones been released yet?

 

Next time it happens, take off the mag and open the receiver. Check if the valve is getting stuck and WHERE is getting stuck. I experienced a similar problem on game today, the BB wouldn't get loaded but the gun fired anyway, when i tried to rack it i noticed more resistance than usual and when i got to open the receiver to check the problem, the valve was getting stuck on part #117. Don't know how but maybe with so low temps these days the rubber gets too stiff ?

 

has any one used any new type of hop unit on the WE yet?

 

I'm using the "modified" hop-up from Stinger/Ra-Tech, it works beautifully for me, it's shoots straight even with .20g bb's.

 

EDIT.

 

Holly ###### ... my writing skills today are sheite

Edited January 10, 2010 by danielsilva

[kojak]

New mag to the left, old to the right (with lid unscrewed a bit due to trying to fix leakage :/).

Stainless (or similar) vs. brass and profile is slightly slightly different. Internally it's quite a bit different, but since all is working so well atm, I won't disassemble the valve for ya ...

 

Whoa, thanks for the photo of the new CO2 valve! The bad news is that I have eight of the old style, and only half of them don't leak at all.

[Bamse]

hmm, today after shooting a mag or so my bolt-return became really slow. Both when firing and releasing the bolt manually it's, well .... just quite a bit slower.

I've checked the #122 status (and general postition of the whole piston and rod), and making sure that the buffer retention hasn't unscrewed it self. I also made a general re-lube and an overall check ... but I can't seem to find anything that's wrong or worn and torn.

 

Any tips? >_<

Edited January 10, 2010 by Bamse

[rvp69]

hmm, today after shooting a mag or so my bolt-return became really slow. Both when firing and releasing the bolt manually it's, well .... just quite a bit slower.

I've checked the #122 status (and general postition of the whole piston and rod), and making sure that the buffer retention hasn't unscrewed it self. I also made a general re-lube and an overall check ... but I can't seem to find anything that's wrong or worn and torn.

 

Any tips? >_<

 

check to see if the nozzel is not sticking in the forward position,the nozzel head/tip could do with a lite sand..

[Bamse]

Well, it's the return of the bolt from the backmost position, so I doubt it's that tbh :/

[rvp69]

oh ok, still its worth a check to see if it is releasing (when cocking it) if the nozzel is sticking in the forward position it may hinder the bolts return?

[3vi1-D4n]

It depends which rubber in the system that is causing the issue. It is a complex error.

 

1) The O-rings (There are 2 O-rings) on the stock CO2 nozzles are oversized, and pushes against the walls of the brass chamber, this is issue one. On the first few rounds of a fresh magazine, the friction is overcome by the sheer force of the blowback.

 

2) The nozzle end is designed to securely lock in with Part 112 because of the shape of the nozzle and part 112, and requires a small force to pull this out. Normally this is a good thing because creates a good airseal, but coupled with the tight O-rings in 1), means that each blowback cycle requires more gas to overcome the frictional forces in the system.

 

3) Because it requires more gas to push the bolt back it cools down a lot faster.

 

3) After prolonged rapid firing, part 112 shrinks from cooldowned gases lowering its temperature. Part 112 grips and tightens around the nozzle a lot more and increases the forces required to pull the bolt back.

 

4) At this time, the blowback is weakened due to the cooldown, so insufficient kick is present to overcome the frictional forces in the system applied to the nozzle. The gun does not chamber the next round.

 

5) At this time on some older WE M4s, the one way O-ring sleeve on Part 121 increases in size (from the pressure) and increases friction between the blowback system and the brass chamber.

 

6) Because the frictional forces are always present and increases during the firing cycle, the tensional stresses on the 3 prongs of the nozzle fractures the nozzle head over time.

 

The solutions are simple. Its a matter of getting the right dimensions in the rubber parts.

 

- Dremel Part 112 to open up nozzle a little.

- Sand down/dremel down the nozzle (CO2) to smooth out the bumps on the front of the gas nozzle

- Remove the first O-ring (smaller one) on the nozzle (CO2)

- Test fit and carefully dremel the 2nd O-ring, all over with a sanding bit.

- And if necessary carefully dremel part 121 O-ring/sleeve to fit into brass tube.

 

Basically the whole BCG/nozzle/blowback system should be able to move in and out of the brass tube/hop unit with no felt friction at all while all the O-rings are still sealing gas.

 

Lightening the BCG also helps minimise cooldown. Its about efficiency.

 

More efficient in the blowback system less issues you will have.

Edited January 11, 2010 by 3vi1-D4n

[renegadecow]

Have you tried cleaning and lubing the operating rod of the nozzle? I had mine gunked up a few times and it slowed down the bolt on the return stroke.

[Bamse]

Hmm, when u mention it ... That's actually one of the few things that I've touched that could cause this.

Earlier I've used shooters grease on the #39 rod and a few days ago I wiped it clean and tried some silicone RC shock oil (like 100 or 110wt) since the action was a lot more smooth with oil than grease. Pun not intended, but simulating the stroke with oil it feels like, no friction at all ... like fluid on fluid action.

With grease there is a much more metallic grinding feel to it. Not excessive or bad in any way, but I just liked the oiled up action more.

 

I can definitely see high weight oil making the return this much slower. Gonna try wiping and greasing it again when I get home from work.

[kojak]

I also have some intermittent resistance on the return of the bolt: if I rack the charging handle slowly the bolt will sometimes just stay to the rear until I tap it. I'm using dielectric grease, which is not quite as slippery as silicone oil but shouldn't cause enough friction to keep the buffer spring compressed.

 

I have a very early model M4 converted to CO2 and I suspect my buffer spring has either weakened over time or been phased out by WE for something a little stiffer. The bolt does not cycle slowly when fired or racked quickly, but occasionally locks up when fired by travelling too far back, which I think may also be a symptom of a weak spring.

 

I'm lengthening the buffer stop to deal with the jamming issue. Is there a way to determine the correct maximum rear travel?

[3vi1-D4n]

I am actually using a weaker AGM buffer spring on mine.

 

Have you changed the charging handle? Before I changed the buffer spring, I once changed my charging handle to a steel one, and the bolt seized up to the back during the firing cycle. I replaced it with a reinforced aluminium one and it has been working fine.

 

The charging handle dimensions were a bit off for the steel one which allowed the rear of the bolt is being pushed up to the side of the buffer tube hence creating the seizing issue. If you haven't swapped charging handles or your seizing only occurs during prolonged firing then its not the charging handle issue.

[kojak]

I'm using the reinforced WE charging handle too; I couldn't get the real one to fit no matter where I filed it. Are you saying the inside was too thick where it contacted the roller?

[danielsilva]

3vi1-D4n aren't u refering to part #117 ? Or are we using different diagrams, cause part #112 is the rod housing ? Anyway that was the problem that i encountered, the nozzle was getting stuck in part #117 due to various ( freezing, low lub, dirt ), even when full of silicone and clean the nozzle would encounter enough resistance to not chamber the next round. Solution was really to dremel part #117 and the nozzle a bit. I'm actually trying to find a better material at work that does the same job and is a bit more cold resistive.

[3vi1-D4n]

Kojak: It "may" be one of the possible causes.

 

To test, find a stock M4 and take the cocking handle fit it onto your BCG and receiver, and try cycling the rifle. If it doesn't seize up compared with your cocking handle then you know your cocking handle is at fault.

 

Else it would be a whole host of the other rubber issues causing it to seize up.

 

Daniel Silva: Yeah I mean the rubber sleeve thing...Listed on AB as 112...I didn't get a diagram. I bored mine out as well as sanded down the sides of the tip. Works fine, no misfeeds no seizing even after rapid fire.

Edited January 11, 2010 by 3vi1-D4n

[renegadecow]

Is there a way to determine the correct maximum rear travel?

As long as the roller on the hammer still makes contact with the track on the bolt, it's still ok. It's when it goes past it that you might have a problem.

[kojak]

Well I learned the hard way that the tolerance for the buffer depth is pretty tight--too deep and it instantly locks up, not deep enough and it won't cycle. I ended up adding about 2mm to the thickness of the stock buffer stop--seems to have solved my problem with the bolt jamming to the rear, and now my bolt locks back on an empty mag much more consistently (not sure why that happened).

 

I created a new problem: with the fire selector on "auto" the hammer won't stay cocked, and the firing pin won't retract. I have the CNC trigger group installed, but it was working fine up till today.

[renegadecow]

That... doesn't make much sense. The firing pin and auto sear are completely independent from each other only that they're both actuated by the hammer. Maybe your hammer isn't going down enough? But the bolt pushes the hammer down to full depth at a mere 1/2 of its stroke. Now that I think about it, I remember someone here having a similar problem with the hammer not going down enough and was found to be cause by the channel on the charging handle being too high. Can't remember if it was fixed by adding material on the groove or swapping the roller bearing with a larger one.

[3vi1-D4n]

If the firing pin does not retract on auto, it means that the firing pin disconnector may be broken.

[[BS]_MARS]

Has anyone tried to use quality lubricants which are typically used on real firearms, i.e. Slip 2000? I'm curious about their effects on GBBRs.

[renegadecow]

"Formulated with out the use of mineral oil or petroleum distillates SLiP2000™ EWL has extremely high penetrating and (EP) antiwear properties."

 

I suppose its safe.

[Anasaan]

Hello,

 

I would like to know if a PTW's Stock is suitable with our airsoft gun.

Thank you.

[kojak]

Just get yourself any mil spec stock, I think Systema uses a size in-between military and commercial diameter.

 

That... doesn't make much sense. The firing pin and auto sear are completely independent from each other only that they're both actuated by the hammer. Maybe your hammer isn't going down enough?

 

If the firing pin does not retract on auto, it means that the firing pin disconnector may be broken.

 

I took a closer look at it last night; it just wasn't cocking completely in auto, the firing pin functions normally.

 

Turns out the auto sear (part #48) was slightly bent, probably thanks to the jamming caused by the bolt going back too far. I thought I had found the root of the problem, but when I straightened it out the receiver halves wouldn't fit together!

 

I've watched the video on the M4 wiki dozens of times, but does anyone have a clear photo of what the auto sear normally looks like with the lower assembled?

[RayL]

Turns out the auto sear (part #48) was slightly bent, probably thanks to the jamming caused by the bolt going back too far. I thought I had found the root of the problem, but when I straightened it out the receiver halves wouldn't fit together!

 

 

Try moving the fire selector to "semi" or "safe" before closing the rifle. Usually if it's set on "auto" the receivers wont close completely.