M4 trigger issue

[Cyclops]

Re: M4 trigger issue

Hi yh it's a src sr4a1 it worked ok before apart from a dodgy trigger switch , gears look ok maybe I've done something when ive put it back together

[Sitting Duck]

Re: M4 trigger issue

Normally you fit box back and affix in this order:

main receiver pin (though this passes through top receiver) and small tiny gearbox pin
then fit grip to box with motor & plate
finally stock tube is fitted

That way the box "shouldn't" be misaligned from being pulled slightly out of tru alignment with nozzle to hop bucking
However it can still happen and can hard to pinpoint exactly why it doesn't align correctly like before

What else did you touch inside box, the switch spring if fitted incorrectly can rub on tappet plate moving back n forth

assuming nothing else got changed it sounds like the nozzle is not fully sealing against bucking so the stock tube might have started to pull the gearbox back and even upwards a little - not sealing and rubbing on hop unit rather than sliding freely into hop sealing against rubber 101%
normally you would not get feed issues as this is normally down to nozzle not clearing the mag feed tube correctly stopping bb loading into hop and failing to load into the bucking.....
but bent bucking lips can cause feed issues, and often people think guns double feed but this is not normally the case

good gun goes: 1 - 1 - 1 - 1 - 1 - 1 etc....

bad gun goes: 1 - 1 - 0 - 2 - 1 - 1 - 0 - 2 - 1 etc...
the bb fails to fully load or fire out of bucking/hop ( 0 ), another bb loads and does fire - so you get 2 shots come out from it misfeeding on the previous shot

you can check the spring on the hop unit is still there trying to apply pressure to box/nozzle to seal ok
you can stick a piece of card in front of hop to push it backwards a small tiny bit also

But normally - pah what's normal about the pesky toy guns, normally I have found fps drop still feeds ok
it is when the nozzle is sealing great against bucking it doesn't quite have enough clearance of nozzle magwell to load bb's well on full auto

I'm wondering if tappet plate is moving ok and its spring is doing well to load bb's into hop
but first see if hop unit - might be a 2 piece unit is sealing ok and pushing back to box correctly
also if it is a 2 piece - check the lower half is fitted correctly and guiding the nozzle straight into hop unit
it could be out of whack and restricting the fast rapid movement of nozzle to load bb, pushing into bucking and sealing great in a rapid blink of an eye

something is deffo out of whack, check everything outside the box first coz sounds like something has gone out of alignment to me
double and triple check everything before you rip her all to bits again.

What I meant by the gears - the metalurgy cheapo src gears have very thin sector to spur gear width, with a bit of play/wear they get very little teeth contacting each other and can miss and cross causing a box lock-up. the bevel & spur are not too bad but had 2 x cheapo src sectors fail this way
replaced with a better shs sector and you can see the difference - like I said these src's are not so outstanding like the other 2 makes

but it still was nice gun while it lasted

[Cyclops]

Re: M4 trigger issue

When I took top reciver off I had to take outer barrel out to get wires out and when I put back together I noticed a spring and didn't know if I came out of the barrel or just my spare 1 lol so I will check the spring on hop unit ☺

[Sitting Duck]

Re: M4 trigger issue

Yeah reckon that is where most of ya problem is

Should go on top of hop unit, slide barrel out and you will see, some m4 hops don't always have/need it most do and then there is o-ring and other mods too

Looks like it came out of a Biro pen but helps to seal or keep hop pressing back on gearbox/nozzle

Welcome to meccano world of toy guns

[Cyclops]

Re: M4 trigger issue

Well at least I now know how to assemble and dissasemble a m4 lol think I will get little bits at a time for it first will have to be railed hand guards not to keen on the standard 1 , and defo a sight as I don't like the iron sights on it lol

[Sitting Duck]

Re: M4 trigger issue

All sorted ???

Hey wtf, you just experiencing same grief we all had when first having a go at " fixing " them poxy mofo guns

[Cyclops]

Re: M4 trigger issue

Lol I will take a look in morning to see if it is the spring and if it is I will put it back then test it fingers crossed but would that cause it to lose power , I would of thought at 30ft it would make a hole in a coke can as when it had the trigger issue I had it chrono and it was 317 fps

[Sitting Duck]

Re: M4 trigger issue

The hop/barrel can shift forward as nozzle pushes bb

Just a whisper of a mm is enough to allow air to pi$$ out and hardly any energy will be sending that bb on its way

99% sure that is problem or the main problem

[colinjallen]

Re: M4 trigger issue

I would think that the absent spring is almost certainly the cause.

As Sitting Duck has said, the SRC M4A1 is an ok gun, but not a great one; use it until it dies (those green plastic bushings will give at some point, unless the sector gear disintegrates first) and then upgrade to a better one.

Airsoft guns are badly designed and most of the internals seem to be made of cheese; they go wrong for all sorts of strange reasons and often take a lot of experimentation and swearing to get them working properly again!

Welcome to the hugely frustrating world of the amateur airsoft fixer.

Now, if anyone can explain why my MP5K occasionally shoots a round which is about 80fps lower than usual, I will be most grateful. The gearbox is spot on, everything moves as it should, the hop unit is as close to perfect as I can get it and the barrel is as clean as an archbishop's conscience, yet it still drops the occasional low one!

[Cyclops]

Re: M4 trigger issue

Ok cool I will update you tomorrow hopefully it works as can't afford a new gun , I got this for peanuts lol

[Cyclops]

Re: M4 trigger issue

Right it was the spring off the hop up I found lol so input that back on and it sounds more powerful but now I'm having the same issue with the trigger like I did before but it's a new switch and wiring I've also pulled the main spring out and pushed the plunger in whole covering the nosal with my thumb and it goes down and I can hear the air coming out which I was told is not right lol

[colinjallen]

Re: M4 trigger issue

You have an air leak��. Take the nozzle off and try again with your thumb over the tube on the cylinder head. If all is good, the problem is at the cylinder head/nozzle interface and you should probably get a better quality nozzle with an internal o ring. If it still leaks, it is either the cylinder head seal or the piston head o ring. Try greasing up the cylinder head/cylinder interface and trying it again.

Is the cylinder ported? If so, which end is the port?

[Cyclops]

Re: M4 trigger issue

I've tried without being connected to the tapet plate ( think that's what it's called) and it's really hard the push but when it's coneected back on it losses air

[Sitting Duck]

Re: M4 trigger issue

OK from memory here is a run down of src box....
you probably have a metal box with 6mm green plastic bushings
you probably have a full cylinder (brass type) with no holes or ports in it
but you have got a real crap nozzle no o-ring in there - plus side I think your cylinder head is a double o-ring one perhaps
green piston etc....

what this all means it is overvolume but with a piss poor nozzle seal on cylinder head - but would probably work out about right-ish anyway on 363mm barrel

you can fit an o-ring nozzle to make it ultra efficient, clean & polish cylinder with silicone oil buff polish it
then smear silicone grease on piston o-ring etc... to improve seals
bare cylinder and cylinder head with piston should seal very nicely - if not and head is loose ptfe tape it (cylinder head btw)


Onto trigger problem......

you have fitted a shs switch which is a good switch and doesn't need copper plate on selector switch to make contact with switch
shs switches don't have the 2 x prongs at rear of switch - or they shouldn't last time I checked
(this is an area that gets overlooked if prongs actually make contact with selector - but shs don't have them so this can be ruled out)

NOW I really am hoping that your trigger is not stuck in dead zone
by this I refer to a point where on semi the cut off lever by switch is trying to disengage - well yank switch up to fly back after single shot
this dead zone of cut off lever raised will not allow you to pull trigger in semi - DO NOT FORCE IT

If you find it is in dead zone - clicking on semi, then switch to auto fire a shot or two and then try again in semi
This can happen if you release the trigger a smidge too early when firing on semi and it comes to rest in this spot
normally the gun would disengage properly and the sector gear with a cut off cam on it goes past the dead zone as it comes to rest

OK - now try the gun on auto - still clicking ??
or does the clicking only happen on semi ?
it might need a small file/mod to ensure the switch slips under the cut off lever on semi

OR if still doing this on semi and auto especially when trigger fully pulled then the trigger itself is not fully latching onto the switch

There is a lug on the trigger itself, usually it doesn't wear but sometimes this lug can be a little short
I have had to replace one in quite a new gun coz it kept slipping off the switch

Also worth noting the spring on the switch should be fitted the correct way round
the coils of the spring should be as low as possible to prevent rubbing on tappet plate and ensuring switch comes back to rest straight for trigger to relatch onto

What I suggest is to carefully examine how the switch operates and you may find the reason why it isn't engaging correctly or jumping off or slipping off the switch

A lot of people think their gun is boned but the dead zone is a common new comers lesson to learn
or trigger discipline as it its called - it would be nice if it was just that but if not

then afraid more gearbox opening to find out what exactly is not operating 101% correctly

[Cyclops]

Re: M4 trigger issue

The new g&g trigger switch does have 2 copper prongs , I need a new piston a well as I noticed it's missing teeth and some have worn down lol