Cursed gun: inconsistent shots untill it "heats" up

[Baff]

First,hello there! I've been having issues with this gun for 7 months already,been using it but it keeps frustrating me that its not working how it should. It was Specna Arms E19 with its orion gearbox...poop gearbox cracked,replaced it with  retroarms cnc gearbox and thats when problems started...one would think ok thats the problem,all the parts are the same from old gearbox and what changed is the shell...but i tried different shell aswell,same problem. Can't find anyone else with same problem. Today got sick of it and decided to make a video and either fix the problem or sell everything and give up on all tech work and just plant potatoes in my garden and live a simple life.

 

Opened up quite a bit of gearboxes v2,v3,v6 in the past 2 years,they all ended up working ever since...but what i cant fix is my own gun

 

 

1st shot low fps
2'nd shot good fps
next shot-low
next shot-good
etc...

 

Untill i spam semi/full auto and after that it is alright for awhile(untill i stop shooting for couple of minutes)

Curent build on M4 MK18 Specna Arms E19:

Jefftron Leviathan with active braking and cycle microswitch,so the cut off lever is out
Barrel: 6.02 Stainless Steel 270mm ZCI,same problem on stock barrel aswell
Gearbox: Retroarms CNC V2 Gearbox
Maxx hopup: tried changing to 2 others >same outcome
HOP UP: Maxx adjustable nozzle - tried 3 others m4 nozzle, >same outcome
Bucking: Maple leaf macaron 60*(yellow) - tried maple leaf green and madbull red shark > same outome
Gears: 18:1 short stroked gears - tried 2 other sets and without short stroke > same outcome
Spring: M130 > same problem with weaker ones and non-SS gears
Tappet plate: Reinforced Tappet Plate V2 [FPS SOFTAIR] Orange - Tried stock and 2 others
Motor: Tornado F1 High Torque Gen.2 Motor,same problem with stock motor
Cylinder: stock SA,tried 2 others
Piston: SHS blue one with metal teeth
Piston head and cylinder head are mushroom type,had same problems with stock aswell

 

-Changed o-rings on everything,compression is excellent(when i hold the nozzle with finger and push piston)
-Tappet plate is moving freely inside the gearbox,not getting stuck on something as far as i can see
-Different mags dont make difference either
-Praying in front of the gun didnt do anything either

The main mistery is that it shoots 1 good,1 bad,1good etc...untill i have a feeling something "heats up" and then it shots perfectly every hit...if its some mis-alignment or tappet plate issues it would keep on being broken and not get "fixed" once i get frustrated and shoot a bit xD

Open to ANY suggestions,can quickly open up gearbox and take pictures and check whatever needed as long as it makes sense. Posted on couple more forums/threads so will update quickly if there is progress.

[concretesnail]

Have you tried running it all with braking off?

 

[Baff]

12 minutes ago, concretesnail said:

Have you tried running it all with braking off?

 

I tried it before.

 

And because you took your time to suggest it,turned it off right now,same outcome. And also same stuff when i shoot a 15-20 bbs,its alright then. so same with and without Active Braking.

[concretesnail]

If the braking isn't an issue something else is affecting how the nozzle seats when the piston drops. 

I'd look change the maxx units out for something else and also look to change the spring that pushes the hop unit back to the gearbox.

It could be combination of things like the feed tube slightly lifting the hop away or spring not strong enough or long enough to reseat the hop chamber

Edited January 21, 2022 by concretesnail

[Cr0-Magnon]

May sound silly but have you checked your chrono is reading as you'd expect it with your other guns?

 

I had one that started giving seemingly random readouts. At first I thought it was the gun but bought another and was getting the results I expected.

[Baff]

17 minutes ago, concretesnail said:

If the braking isn't an issue something else is affecting how the nozzle seats when the piston drops. 

I'd look change the maxx units out for something else and also look to change the spring that pushes the hop unit back to the gearbox.

It could be combination of things like the feed tube slightly lifting the hop away or spring not strong enough or long enough to reseat the hop chamber

I have just mounted a different set of barrel,hop,bucking,air seal is terrible but the outcome is similiar.

 

1 shot 1J

next shot 0.4J

next shot 1J

next shot 0.4J

 

trigger spam like before 10-15 shots,every next shot is 1J

 

So would that be the same problem i guess with aditional other ones and a proof its not a hop,barrel.

 

Also with maxx hop i tried 3d printing some small spacers to put between hop and upper reciever(to push the hop flush to the gearbox) and the problem was the same.

Also the maxx hop i have has that extended "ring" with o ring and it fits inside/around the gearbox flush AF.

 

[Rogerborg]

Having carefully read everything that you've written and tried, then I'd concur that it's either the chrono, or you should accept that it's time to live the life potato.

 

Honestly, you've ruled out everything that I can think of, short of swapping in another complete gearbox to see on which side of the nozzle the problem lies.

[Baff]

6 minutes ago, Cr0-Magnon said:

May sound silly but have you checked your chrono is reading as you'd expect it with your other guns?

 

I had one that started giving seemingly random readouts. At first I thought it was the gun but bought another and was getting the results I expected.

Nothing is silly brother,its damn vodoo. I think the chrono is reliable,shows everyone elses consistent fps...but nonetheless i just loaded my p90,turned on chrono,consistent AF.

 

Switch to cursed m4,same bbs > inconsistency.

 

2 minutes ago, Rogerborg said:

Having carefully read everything that you've written and tried, then I'd concur that it's either the chrono, or you should accept that it's time to live the life potato.

 

Honestly, you've ruled out everything that I can think of, short of swapping in another complete gearbox to see on which side of the nozzle the problem lies.

Potato lyf for me.

BRB gonna go change everything from 1 gearbox to another so we can rule that out...again xD

 

Thanks for replies guys ❤️

[Asomodai]

Are you using Mid caps filled to the brim when testing? 

As this does sound like midcap syndrome 

Edited January 21, 2022 by Asomodai

[heroshark]

Have you done the sacrifice with the herbs and incantations.

[Baff]

5 hours ago, Asomodai said:

Are you using Mid caps filled to the brim when testing? 

As this does sound like midcap syndrome 

It seems to be a weird midcap syndrome. When mags are almost empty,little to no fps deviation,when they are full,it happens...tried before many different parts and it was always the problem.

 

When nozzle is fully out,by touching it i can see there IS a bit of possible wobble up/down. So i've put SHS cylinder head and the nozzle for it,and when its pulled out theres WAY less wobble and looks like it is alright,i also shortened my tappet plate spring by 2 coils.AAAAAnd again 1 shot is 1.5J but the 2'nd one is at around 0.9 now instead of 0.4 like before.

 

So now its 1.5>0.9>1.5>0.9 etc... untill the mag is almost empty then they are all 1.5.

 

So less wobble > less deviation in J.

And i guess that is a typical case of midcap syndrome. Any other ideas how to fix it? Order another cylinder head and matching nozzle for it and hope its alright? Stronger tappet plate spring? 

[Asomodai]

17 minutes ago, Baff said:

It seems to be a weird midcap syndrome. When mags are almost empty,little to no fps deviation,when they are full,it happens...tried before many different parts and it was always the problem.

 

When nozzle is fully out,by touching it i can see there IS a bit of possible wobble up/down. So i've put SHS cylinder head and the nozzle for it,and when its pulled out theres WAY less wobble and looks like it is alright,i also shortened my tappet plate spring by 2 coils.AAAAAnd again 1 shot is 1.5J but the 2'nd one is at around 0.9 now instead of 0.4 like before.

 

So now its 1.5>0.9>1.5>0.9 etc... untill the mag is almost empty then they are all 1.5.

 

So less wobble > less deviation in J.

And i guess that is a typical case of midcap syndrome. Any other ideas how to fix it? Order another cylinder head and matching nozzle for it and hope its alright? Stronger tappet plate spring? 

 

To be honest the only sure fire way is to wear in the spring on the Mag. Or go for weaker sprung mags/high caps.

Edited January 21, 2022 by Asomodai

[concretesnail]

You could try a work around/test by binding the base of the spring in the mid caps. Compression a few coils and the wire them together, you'll loose some capacity but find a coil count that works for your need feeding pressure and then cut raw springs to that number of coils.

[Rogerborg]

7 hours ago, Baff said:

BRB gonna go change everything from 1 gearbox to another so we can rule that out

 

Erk, no, I mean, if you have another complete V2 gearbox to swap in, I'd try that, not moving parts around.  At this point it seems like you'll want to binary-chop the issues down rather than introducing new variables.

 

That said...

 

2 hours ago, Baff said:

It seems to be a weird midcap syndrome. When mags are almost empty,little to no fps deviation,when they are full,it happen

 

One piece of voodoo that (maybe) helped me with an inconsistent feed issue was putting a detent into the top of the hop chamber.

 

Take a 6mm drill bit, put it straight up the feed tube, and very carefully create a small relief in the top of the chamber.  With a plastic chamber, I did it by hand, with light pressure and a few turns.  Just enough to create a shallow dome that the BBs can key into and feel safe and loved rather than finding themselves unsure where to go.

 

I'm unclear on the science (if any) behind it, but after doing that, my feeding problems went away.  Although with it being airsoft, its just as likely that they were sorted by sheer fluke by yet another disassemble-reassemble.

[Baff]

10 hours ago, Rogerborg said:

 

Erk, no, I mean, if you have another complete V2 gearbox to swap in, I'd try that, not moving parts around.  At this point it seems like you'll want to binary-chop the issues down rather than introducing new variables.

 

That said...

 

 

One piece of voodoo that (maybe) helped me with an inconsistent feed issue was putting a detent into the top of the hop chamber.

 

Take a 6mm drill bit, put it straight up the feed tube, and very carefully create a small relief in the top of the chamber.  With a plastic chamber, I did it by hand, with light pressure and a few turns.  Just enough to create a shallow dome that the BBs can key into and feel safe and loved rather than finding themselves unsure where to go.

 

I'm unclear on the science (if any) behind it, but after doing that, my feeding problems went away.  Although with it being airsoft, its just as likely that they were sorted by sheer fluke by yet another disassemble-reassemble.

 

I have 2-3 plastic hop ups aswell,can try one and see what happens.

 

You meant on very top(on picture #1 spot) or top of the feeding tube(picture #2spot)?

 

As for wearing down mags,i've been using these same mags for 18 months already(last 9 of those months i've been having issue) so if anything they should have been broken in so far i guess 😕

[Adolf Hamster]

i have had this before, guns that would barely spit out bb's at chrono only after a couple dozen shots spend the rest of the day exactly on point (i've also had the inverse- guns that would chrono perfectly then proceed to fall flat on their face the moment there was an actual target to shoot at)

 

one possibility is gearbox alignment, if the nozzle is scraping the hop such that it'll stick the first few times then be ok. although this should be evident by any wear patterns on the nozzle.

[colinjallen]

11 hours ago, Baff said:

 

I have 2-3 plastic hop ups aswell,can try one and see what happens.

 

You meant on very top(on picture #1 spot) or top of the feeding tube(picture #2spot)?

 

As for wearing down mags,i've been using these same mags for 18 months already(last 9 of those months i've been having issue) so if anything they should have been broken in so far i guess 😕

I had a similar problem which I suspected was due to the nozzle being marginally too long. I slightly filed down the right angle just above the blue blob in your sketch; it seemed to give just enough room to enable the BBs to enter the hop unit without interfering with the nozzle.

However, you seem to be using a Maple Leaf Macaron; the feed lips on these are marginally too long for some hop units, which can cause a similar problem to the one you are describing.  Gently sanding them down a bit at a time and constantly checking tends to cure the problem.

 

 

 

[Rogerborg]

13 hours ago, Baff said:

You meant on very top(on picture #1 spot) or top of the feeding tube(picture #2spot)?

 

Spot 1.  Drill bit straight up the feed tube.  Left is raw dogging it from the factory, right is the ordered perfection that I imagine I've created.

 

 

That said, Luke at Negative has just advocated smoothing away spot #2 to help with feed issues, and I can see the point of that as well.

 

I can only speak to what I've tried though, and a gentle penetration straight up the feed tube seems to have helped me with problematic feeding.