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The Joke

CM16 missfiring?

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Hi all, I could use some help with my rifle.

It's a G and G CM16 of which stopped working for a little while because the internals were in the wrong positions. That's all been fixed, but now there is a new issue.

When I hold down the trigger, it takes about 2 or 3 shots for a BB to actually come out of the end. There is air blowing out of the end when I am firing, and the magazine is fine. I'm worried I may have done something when tinkering around inside of the gearbox.

Any help you guys can give would be really appreciated.

Thanks!

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CM16 of which stopped working for a little while because the internals were in the wrong positions.

That's all been fixed, but now there is a new issue.

When I hold down the trigger, it takes about 2 or 3 shots for a BB to actually come out of the end. There is air blowing out of the end when I am firing, and the magazine is fine. I'm worried I may have done something when tinkering around inside of the gearbox.

Any help you guys can give would be really appreciated.

Thanks!

 

 

Hmmmm - bit vague as to what you did exactly.....

Internals in wrong position - shimming out or something else ???

 

been fixed but new issue - then it is not fixed

 

OK enough of smart ar$e stuff - but please enlighten us to as what happened and what you did so far...

 

Mis-feeding is a result of about 3 main issues but can be down to one of at least half a dozen parts - or a few of them at same time

 

The bucking or rubber in the hop can become tight/damaged/bent at the lips and not allow a bb to pass into barrel easily

(there are more things to check but I'm gonna go ahead and presume you haven't messed with hop/bucking)

 

The tappet plate holding the nozzle and its spring are the next main areas that can cause misfeeds if they are worn or not operating correctly

If the nozzle gets changed it MUST be of a similar or very close spec/size to the original

If tappet plate wears on rear fin the tappet "window" will be reduced and nozzle will not clear to allow a bb to chamber or start to pass into hop unit

If spring is weak it will often not feed well in auto

(actually it is quite common that guns feed ok or reasonably ok in semi but on auto feeding really starts to struggle if it isn't all in good working order)

 

Magazines - some mags are better than others and some guns may only work with certain mags & vice versa

 

There is more - but I tend to think you may have opened the gearbox maybe and something has either worn or been replaced/rebuilt incorrectly

(different nozzle, major wearing of tappet fin or something else)

 

This is a major bit of guesswork atm coz like the theif who stole the toilets from the police station - I have nothing to go on atm

So please explain a little further if you can what has taken place so far

 

PM2qFs6.jpg

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I had to strip the entire gearbox apart and put it all back together. I'm afraid I can't exactly remember the reason why it wasn't working, but it wasn't firing at all. So it's quite possible that things were shifted about. I also put in a completely new spring, so I doubt that is the issue.

 

So far I've turned down the hop up to see if that'll fix it, nothing happened. I haven't dived into the gearbox yet, but I get the feeling I'm going to have to.

Is there any way for me to tell if something's worn down or not working properly?

 

Thanks for the quick reply!

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Well I'm no expert - I'm still learning by my numerous own mistakes

and seems I learn more n more with every box I fix or usually have to reopen again coz something isn't quite as expected

 

I listed off the main common reasons for feeding issues and bits wearing/failing

 

could be tappet/nozzle related but is really impossible to guess

It could also be that the box is sitting a bit out of whack......

normally you replace the 2 pins large and small taper pin, then refit the pistol grip and finally the stock tube once the box is secured

As this is all done you can get the box being pulled slightly backwards which can tip the from of box/nozzle upwards

this can mean the nozzle may now scrape or rub inside hop as it attempts to chamber bb's

and/or the seal can be slightly less than perfect - but often if box & hop are out of whack & not aligned you can get more problems

 

If there has been a lock up and box seized at some point - the tappet fin at back could have got a bit of extra wear on it

V2 boxes very often have less overall travel of nozzle tappet than say v3's

This means you may have a max 8mm movement at very best - you need 6mm to clear a bb, but probably another 1mm at least to seal with bucking

plus about 0.5mm to be on safe side = 7.5mm of nozzle movement and that is if you are bloody lucky right on the min limit of the "window" being bang on 101% in the exact place for all round perfection.

 

not enough retraction - feed problems as bb won't chamber

too little final extension and pi$$ poor seal on bucking

 

So this needs to be checked when you finally open box or send it to a tech maybe if push comes to shove

 

However - I strongly advise checking the hop is ok first.....

 

take out barrel & hop unit, wind off the hop to very very little, drop in a bb and it should just stop in front of bucking...

Now it should need only light pressure from a screwdriver or cleaning rod - actually something soft or smooth

see if the bb will pass through the bucking lips fairly easily - if it doesn't there is quite likely the main culprit

if bucking lips are damaged/folded or tight a bb will always struggle to feed

if bucking lips protrude to far fowards they will impede and restrict the best mags in the world chambering a bb every time into hop

 

hard to explain I guess but this vid goes into much more detail - way too much in some cases

(why do I find these tutorials after I have struggled and started to work out crap for myself after numerous failures)

 

Anyway - this shows just what a bitch hop units can be and how to run a few checks....

 

 

PS - I do not advise using dremmel - but the push through test is really what I was referring to

 

Most likely the box will need looking at but this hop diagnostics should be looked into before anybody simply steams in thinking it has to be something else inside gearbox etc......

 

hopefully this might help but have a looksie and test out the bb passing into hop etc....

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