Inconsistent firing...air nozzle? Hop up? Bucking?

[Cleaners inc]

Abit of background on this nightmare gun...

I purchased a second hand G&P m4 cqb with just a basic mosfet fitted. Guy claimed 340fps and “fully serviced”. 

It arrived, chronoed at 270fps but guy promised it was more when I questioned him on the matter. In the end I Gave the gun to a retailer/tech shop and they found the gearbox had hairline cracks, wiring was poor and air nozzle wasn’t much good.

so work done by retailer:

-rewired

-new gearbox casing 

-new air nozzle

Guns now firing at 340fps, sweet! However was not impressed with the rebuild quality as fire selector is sloppy, doesn’t click into semi or auto like before and can sometimes (rare) even fire full auto on semi. Wasnt doing this before burn i can live with it

The main issue is inconsistent firing and poor range making it extremely annoying to play with. some b.b fire okay and straight, some fire completely crap and just flop within a few metres, others go up, basically the flight path of my B.B. are all over the place and the overall range seems poor compared to any other gun I’ve ever used. the hop up does affect flight path and seems to work but doesn’t stop any inconsistancy.

This has been tested on .20 and .25 without any difference. I’ve dismantled and rebuilt the hop up and can see it working and pushing the bucking down 

Is this a hop up/bucking issue or am I right in thinking my air nozzle isn’t working as it should?

*please see video*

not majorly clued up on gearbox workings but I compared this to another m4 I have that works faultless with decent range and the nozzle always stops in same position, however with this one it doesn’t? Is this normal? Is this causing the random poor flight paths?

as you can tell I’m no expert so advice is greatly appricated.

Id rather not take to a shop as only local shop I wasn’t very impressed with for multiple reasons, so this is a problem I’d like to learn to rectify myself 

many thanks 

 

[Sitting Duck]

Air nozzle is fine....

Everybody thinks the nozzle should stop fully forwards on each cycle

but in fact the nozzle has returned to seal against bucking/hop

What is taking place is the drivechain is continuing to rotate after spring is released

and the nozzle is being retracted slightly with the sector just starting to engage the piston

(just starting to retract and take up spring tension)

All the spring tension, first from tappet plate spring when nozzle starts to retract again

then maybe as piston begins to retract - taking the more powerful spring is bringing the drivechain to a complete stop

Why the variation of nozzle retraction ???

why sometimes a tiny bit backwards and other times further retraction

because there is no active braking in which the motor is chucked into reverse polarity quickly stopping the drivechain

With Active Braking though, the carbon can build up on motor, bit more heat etc... but gun stops very quickly & consistantly

sounds a little rough but at least it is cycling

your problem with bb's all over the place & dropping well short....

sounds like a hop/nozzle compatibility issue tbh

the varying shot/range implies the short distance is a leak maybe

the nozzle "looks" like a SHS one which should be long enough to seal against bucking

(some people have trouble feeding in some setups with SHS M4 nozzle)

I would be inclined to start/use another hop/barrel a sec - maybe borrow the hop/barrel unit from other gun a sec

I would suspect that could provide more stable results perhaps and probably indicate the other unit needs looking at

maybe try to source a similar barrel/hop if that be the case

some hops/bucking work better & some just don't with some guns

I would try some basic process of elimination first to narrow down your range/accuracy issue first

the nozzle "seems" to be moving back n forth level, so it should insert & operate straight into hop unit

get nozzle fully fully foward, then offer up either hop unit and insert into the front of box

just the hop/barrel unit......

you should feel say some resistance of about 1mm before hop fully hits home against box....

that is the red nozzle pressing against bucking lips and sealing - if you don't feel this resistance

then there is your potential leak

Even if you feel a slight seal/resistance, you can still get the lips blowing under compression if not 101% perfect

(or poorly aligned nozzle/hop/lips etc....)

I'd try another barrel/hop/bucking combo - maybe in other gun first

then depending on results decide if you or a shop will carry out further checks/work

 

[Iceni]

Nozzle position there is cause by a slight over rotation of the gearbox.

I would imagine that 2 things are contributing to it. Better than average motor, 11.1v lipo.

In most guns with that setup it would be expected that the box will over rotate slightly. It's nothing to be worried about. There are ways to correct it, but provided it's not shooting twice on single shot it's not a problem.

Without having the gun in hand it's hard to diagnose the flyers and inconsistency. There are a lot of factors that can cause both and without a well trained eye it's a process of trial and improvement.

I would start by looking at the bucking in the hop. It might be torn or worn out. If the lips have gone or there is a split it can make a gun do all sorts of crazy things.  Or it might be grease. Hops don't like grease at all and will act very strange if they have lubricant on them.

The hop rubber most advise is the maple leaf 50deg, with the omega nub. It's going to cost you in the region of £20 for the setup. And you will have to fit it, So you need to read/watch a few videos on that.

https://www.ak2m4.co.uk/internal-parts/hopups-rubbers/maple-leaf-macaron-50-aeg

https://www.ak2m4.co.uk/internal-parts/hopups-rubbers/maple-leaf-nub

Clean the inner barrel with alcohol as well. And check it for internal damage. I would expect it's in good condition because you describe random events rather than a constant effect like pulling to a side or constant jams.

The last factor for me would be the airseal nozzle itself. In some models of gun they can and do cause all sorts of problems. You need to check it is the correct length. However I would not look at this until you do the hop as there is a good chance that will fix it.
 

 

[Sitting Duck]

Good shout sir on possible torn bucking.....

(was concentrating on the nozzle concern so much)

OP, bit of running on it fine and perfectly normal

a bit of overspin is nowt to be concerned about & even a bit more is ok too

it is when it nearly double fires or sometimes double fires you need to sort stuff

the over cycling of non AB & the stopping dead stuff from Active Braking mosfets.....

Just go to 0:22 onwards and see the motor stop asap with braking and not so quickly without braking

(the extra posi mosfet added/removed)

 

[Iceni]

I hit post about 30 seconds after you, we basically said the same thing!

Torn bucking would be my guess just based on the fact all events are random.

 

[Cleaners inc]

My other guns nozzle seems to retract fully each time, does that mean there’s a problem with that gun? It’s never double feed or seemed to have any problems however 

Onto the gun with problems...

I have previously had the bucking out(apparently a mad bull bucking), cleaned barrel with alcohol solution ect to try sort this problem but didn’t find anything noticeable with the bucking or barrel.

ill replace the bucking and hop up for process of elimination anyway 

king arms hop up and purple prommy bucking seems to be a well regarded setup for a G&P, how does this sound to you Guys?

thanks for all the inputs 

 

[Cleaners inc]

Also worth noting I run this gun on a 7.4v lipo and far as I am aware the motor is standard G&P

 

[Iceni]

My other guns nozzle seems to retract fully each time, does that mean there’s a problem with that gun? It’s never double feed or seemed to have any problems however

What is the other gun.

The retraction of the airseal nozzle is governed by 2 parts. The sector gears tappet cam, and the tappet plate. The only way to increase the rearward throw is to add a delayer chip that increases the distance from centre on the sector gear of the cam. The whole system needs to be balanced, If you shave the tappet plate to make the nozzle sit further out, by default it makes the nozzle retract less.

Variance between V2/V3 boxes is negligible because they both use the same sector gear design and both have the same amount of throw because of that.

It could be that the tappet plate has been shaved, but if it is feeding then the problem is not with the tappet/sector tappet cam setup.

There is also a finite amount of rearward throw you can achieve. At some point you will hit the cylinder head with the airseal nozzle.

From  your video I'd say the retraction amount was correct.


 

I have previously had the bucking out(apparently a mad bull bucking), cleaned barrel with alcohol solution ect to try sort this problem but didn’t find anything noticeable with the bucking or barrel.

Doesn't mean you didn't split it, install it with an airleak, or just get the alignment out slightly. I would strip the hop. Check the springs and the arms, Check the nub, Check the bucking.

Some of the madbull buckings have tight long lips. The red accelerator type have this design and that can cause problems when the BB's catch and roll the lips upwards on the feed and cause a partial jam. If you can see the lips in the feed tube then try the maple leaf rubber it might correct the problem.

 

king arms hop up and purple prommy bucking seems to be a well regarded setup for a G&P, how does this sound to you Guys?

I wouldn't bother.

The king arms hop is £25 for that money you can be on the way to a better design like one of the rotary M4 hops or a CNC unit. The stock G&P unit should work fine if you get it set up right. Adding more parts from another manufacturer when you already have problems will not always solve issues, Sometimes it just adds other problems.

 

[Cleaners inc]

I have read a few places that G&Ps have trouble with Cnc hop ups due to fitment issues within the top receiver. However I could be wrong 

I will first put my other hoopup/barrel/bucking from working m4 into this gun and see if it changes anything.

if this greatly improves what hopup and bucking would you recommend. Other gun is ics hopup, unknown bucking 

 

[Sitting Duck]

I have read a few places that G&Ps have trouble with Cnc hop ups due to fitment issues within the top receiver. However I could be wrong 

Prowin hop units can either work great or $hit in some guns

not just G&P's

honestly this hop/bucking bollox is a ball ache at times

often people can strip down a ok-ish hop/barrel combo

refit with new bucking that the bucking is smidge tighter pinching the lips and the hole now jams bb's

or a new prowin hop is made slightly different and bucking sits say 0.5mm further forward so seal is crap

or reverse of above sits closer but nozzle doesn't clear to chamber a bb with a fine tolerance feeding window

so it struggles to feed now

FFS - it is why it not unwise to build a new barrel/hop/bucking combo and if all $hit goes mega pear shape

you still got old ok-ish stock one to use whilst you try again with "upgraded" hop/barrel

I'm not an expert on hops/buckings, I've had many headaches getting crap to work at times

when you see a wise expert assemble it all with stuff they KNOW IT JUST WORKS.....

Well they are so good at what they do they MAKE IT LOOK EASY

the rest of us fumble our way through cursing and swearing at this pile of crap is worse than ever

So yeah not all stuff works quite as it should or on the tin in most guns like it SEEMS

Hence maybe try a new combo and/or pop in the other gun's hop/barrel

if that works sweet, then go and get yourself the same stuff for your problem gun

I have spent money and time on this n that and got no joy at all just throwing money at stuff

when in fact I should have applied some common sense & process of elimination first

 

[Cleaners inc]

Will trying my other guns hop up/bucking/barrel in my G&P cause any damage to it if the air nozzle or similar is the problem? Just don’t want to end up damaging my good stuff and ending with two guns with issues ?

 

[Sitting Duck]

All I'm saying is just try the gun or another gun's barrel/hop combo

don't mess with it, just try a few shots that is all

to narrow it all down a bit....

if your box and the nozzle feeds/seals ok - right get something like that then

I doubt if the nozzle is going to go far forward it smashes into the lips and tears it to f*ck

If your are really worried then leave it as is

just buy another hop/barrel/bucking combo perhaps

make that up and see how it goes

it might be a mix n match of old crap combo & new combo that yields best results

It is fine, if ya worried leave one working gun as is and get some more bits to play with

often this tinkering stuff is all about trying & experimenting with stuff to see which crap works best

same as inside the box - many replace everything inside but can end up with more grief

than if they replaced just the crap stuff - finding out later that that std cylinder head wasn't so bad

or new super piston head isn't so great compared to old one

or new gears don't mesh great with stock motor etc.....

Or new motor don't like stock gears or whatever - you get the idea

seen people go nutz chucking in all new stuff that runs quicker but a lot rougher/$hittier than before

fun n games this toy gun crap

 

[Cleaners inc]

Probably Best I just buy another hop up and bucking setup to keep my other gun working spot on.

what recomendations do you guys have in regards to bucking and hopup?

is everyone on the same page with recommending the maple leaf setup mention above?

ive Done my research and prommy purple looks to be a very highly recommended setup as well

 

[Prisce]

The 3 buckings I recommend to people are the ML50, G&G green and Prommy purple. 

Hop units, I like the ZCI Prowin from AK2M4, or the standard G&p usually!

 

[Cleaners inc]

How is the zci fitment wise for a G&P? Looks fair for £19

 

[Prisce]

Couldn’t comment on its fitment in a G&P, but the G&g, ICS and CA that we have fitted them all to work fine.

 

[Cleaners inc]

Zci hop up with a prommy purple will probably be where I head then

Thanks for the advice/tips