Feeding issues

[Callum Hornsby]

First off I'm sorry for making this topic as I'm sure you have all seen and answered similar questions a thousand times before, but after a forum search I couldn't find anything that gave me enough of an answer to be confident in diagnosing the problem.

As some of you may remember a couple weeks ago I had issues with my v2 gearbox not functioning. That's all fixed and the gearbox works fine now but I'm getting horrid feeding issues. Some bb's will fire fine others double feed some dribble out the end and at points the gun just jams.

I have a feeling this problem is originating from one of two places.

One being the gearbox mods I did which are as follows: nuprol 16:1 gears, nuprol hs motor, zci cylinder head, nuprol air nozzle. I have a sneaky suspicion that this new setup is causing the nozzle timing to go out the window but because of the hideous design of the nuprol gear set it will not accommodate a delay chip.

The second being the hop. After inspection of the now 4 year old unit I noticed a tear in my hop rubber right on the nub and thought that must be the problem so being on a tight budget I decided to shave the nub and line thingy off and do a flat hop as seen here:  https://www.youtube.com/watch?v=TbK167v_8Pg Now to my surprise I did a pretty solid job here and the new hop setup had a perfect straight line of rubber exposed when the hop up was applied. Great not only did I fix my problem but got a cheeky diy upgrade at the same time.... Nope ran the gun with the new hop setup and was just the same as before some fired fine some double feeds some dribbles and some jams.

Here is where it gets really weird you would assume this means that the gearbox is the issue but in my frustration to find a fix before running here for help I decided to run the gun without the hop rubber (just barrel clipped into hop unit) and the gun ran as smooth as a whistle firing a 300 round high cap with no miss feeds, obviously the bb's where only going 30 feet or so due to no hop but they were consistent in there flight.

When the gun did jam the jammed bb came out looking like this:

The black mark is what appears to be a light scratch with a black discolouration.

So at this point I'm so lost and with a limited budget don't want to waste what little money I have spare on parts I don't need.

Thanks in advance for any help,

Cheers Callum

 

[Iceni]

When you rebuilt, and installed the new parts did you reshim the gears, and did you replace the bearings?

I'm thinking the tappet plate isn't fully resetting (full forwards position). This can be caused by a few things, but the most common are bearings/bushings that don't sit flush on the inside of the gearbox. Or a poor shim job that is allowing the tappet plate to get caught between the gear, shell wall and shims.

The fact it runs without a bucking is also suggestive of a tappet plate issue. As it's the lips on the bucking that show a bad tappet reset. The airseal nozzle doesn't push the BB past the lips fully, and doesn't seal on the lips. So you get a double whammy, BB with high resistance in the lips, and a poor airseal to propel it. Jam central.

The black mark could be anything, Including the winding mechanism on the mag. It's best to ignore the mark for the time been and ensure the box is right and resetting correctly first. Then come back to the mark if you find the Tappet plate doesn't fix it.




 

 

[Callum Hornsby]

When you rebuilt, and installed the new parts did you reshim the gears, and did you replace the bearings?

I'm thinking the tappet plate isn't fully resetting (full forwards position). This can be caused by a few things, but the most common are bearings/bushings that don't sit flush on the inside of the gearbox. Or a poor shim job that is allowing the tappet plate to get caught between the gear, shell wall and shims.

The fact it runs without a bucking is also suggestive of a tappet plate issue. As it's the lips on the bucking that show a bad tappet reset. The airseal nozzle doesn't push the BB past the lips fully, and doesn't seal on the lips. So you get a double whammy, BB with high resistance in the lips, and a poor airseal to propel it. Jam central.

The black mark could be anything, Including the winding mechanism on the mag. It's best to ignore the mark for the time been and ensure the box is right and resetting correctly first. Then come back to the mark if you find the Tappet plate doesn't fix it.




 

That’s sounds like it may be the root of the issue. I’m still running the stock g&g bushings which protrude into the gearbox about 0.5 mm my shin job is decent but as you say just coz the gears are sitting and meshing happy doesn’t mean the tappet is.

I shall take a look tonight and return with an update thanks for the help.

 

[Davegolf]

You changed quite a few parts there.

If the lack of a bucking fed fine then it is most likely a timing issue, too little nozzle withdrawal time or not enough physical room, the latter commonly caused by to large a bucking lips / incorrectly fitted bucking pushing lips to far into hop unit, or the new nozzle you have is too long.

Suggested above is possible - tappet interference, before taking the gearbox apart you can test this by firing on semi to reset / untension the gearbox, EG the piston needs to be fully home, from there externally you should be able to manually push the nozzle back with you finger, and it should be smooth in motion, and spring back fast.

 

[Samurai]

The bucking is needed to hold the BB in place until the gun fire and keeps the rest of the BBs from feeding into barrel all at once.

That is achieved by a slight resistance when the BB passes the lip of the bucking. If you drop a BB into the chamber and it just rolls into the bucking, then replace the bucking.

 

[Sitting Duck]

NOT A COMPLETE DIAGNOSIS BUT A STAB AT NUMEROUS BITS OF CRAP

did you install THIS nuprol gear set.....

WTF do people deviate from reg gears I'll never know

A bloke had a SR25 feed issue problem using SHS 25 gears with bollox bearing on sector

I'll suggest the same to you as I did him....

put on the old sector gear - then you can slightly increase tappet retraction delay etc...

your 16:1 set will use the same sector gear as a std 18:1 G&G set - or it should

You should have used say a SHS tappet checking it doesn't retract too much hitting the cylinder head

SHS tappets retract a whisker more but "can" bottom out on "some" builds

I presume the Nuprol nozzle like motor is a rebrand of the SHS red M4 nozzle 21.45mm

It is sound but said numerous times V2's tappet/nozzle window to feed/chamber/seal is less than v3's

So everything has to be very close to exact precision

If the bearing is not fully retracting like a delayed reg sector - that is one issue

If nozzle is too long (doubt it your case but you never know) you get feed issues

If nozzle is too short you feed lovely but $hit fps as it doesn't fully seal at bucking

(the lips not seal fully allow lips to blow - drop in fps)

Hop unit/bucking....

the lips can get tight/pinched as restrict a bb passing through to nub

way you check this by dropping a bb into hop and with an allen key/nail/screwdriver/jam rod

push the bb through - it should be very light moderate only to pop the bb through the lips

Some buckings in some hops can be tight fit and pinch/distort the lips that impedes/restricts bb chambering

see here - way ott but somewhere is shows what I'm on about....

Now if we assume the lips are fine and hop is cool

let's try an experiment.....

see if you can make a 0.5mm to 1.0 washer/gasket with ID about 10.5mm

Place that over the mouth of the hop unit where it enters the gearbox and refit

What you have done is shimmed the hop forward - can't go nutz coz mags won't clip into feedtube

but a light shim on the hop unit shifting it forward

make it from anything but just shim the hop a smidge forward

Very likely the fps will drop due to nozzle sealing on lips (now 0.5mm further away)

but don't worry about that a sec - just see if it feeds)

Now try to feed/fire bb's - does it feed better ????

If so the tappet window is out of whack, the nozzle is not clearing enough on full retraction

if nozzle clears the feed tube by 5.95mm - you are going to struggle to feed a 5.95 bb everytime

(Ideally about 6.5mm)

Feeding double feeding and other bollox

rarely does a gun double fire but often tight bucking lips or other jams is the culprit

the bb doesn't chamber properly/gets stuck then another bb chambers and both exit the gun

OMG - it's double firing - it isn't, it is misfeeding/mis-chambering is often the correct term eg:

1 - 1 - 1 - 0 - 2 - 1 - 1 - 1 - 1 - 0 - 2 - 1 etc.......

Just saying often people start tearing into stuff without clarifying where the main problem is

As said this is NOT a full diagnosis of your gun problem but more a collection of suggestions

You need to investigate further and try to self diagnose where the main problem(s) are

not gonna repeat stuff but mention about tappet window crap here:







Now you don't need the shave/mod the SHS tappet in G&G like a Cyma box but explains a bit

of what I mean about tighter tolerances in v2's and where this "tappet window" sits

you have little leeway but need to retract enough to feed but still return correctly to seal at bucking lips

It might come to using old G&G sector gear and a delayer perhaps - don't like them bearing sectors

best of luck - probably mega confused you also but chucking my 2 cents

(more like 50 bucks, but hey ho on the word count)

 

[Callum Hornsby]

let's try an experiment.....

see if you can make a 0.5mm to 1.0 washer/gasket with ID about 10.5mm

Place that over the mouth of the hop unit where it enters the gearbox and refit

What you have done is shimmed the hop forward - can't go nutz coz mags won't clip into feedtube

but a light shim on the hop unit shifting it forward

make it from anything but just shim the hop a smidge forward

Very likely the fps will drop due to nozzle sealing on lips (now 0.5mm further away)

but don't worry about that a sec - just see if it feeds)

Now try to feed/fire bb's - does it feed better ???

Okay so I've experimented. Just made my own little shim for my hop unit and installed it and bammm it worked. Well at least until it jammed 15 rounds or so in so at that point I took out the hop to find the bb jammed like this...

BB is caught on folded rubber (I'm assuming this will mean new bucking on ma shopping list)

did you install THIS nuprol gear set.....

Yes, yes I did. Kinda learnt now why the design is crappy but they will do for now.