Help needed!

[Delmatron]

My friend owns a G&P mk46, says the internals have been upgraded and is running on a 11.1v lipo.

The gun is not firing at all - to me the piston doesnt seem to be 'slapping' if that makes sense...

Pics and vid of gearbox attached

Now I do not know much about internals, and will not have many answers to questions without speaking to him first.

Any help appreciated, and apologies if this post in the wrong thread.

thank you

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[Adolf Hamster]

sounds like something's lost it's teeth, the tappet plate is moving so the sector gear is spinning.

that piston looks beat up but not as bad as my f2000's which was still firing (albeit at about 90fps ), do you have another piston to try?

other possibility is if you've had the sector gear bearings explode would mean it's not engaging properly, although you'd have know by the metal chunks splatted around it's insides.

 

[Sitting Duck]

Piston does not move at all in 2nd movie clip

spring / piston - NOTHING is moving in rear window !!!!

Piston has damage to rack guide, possibly allowing rack to shift under stress

Actually these pistons seem to have this area missing but still don't like it

either way piston is a goner....

AND STOP PUTTING YA FINGER OVER NOZZLE WHEN IT'S RUNNING

You will slow the piston return by blocking the compression and this like a jam can cause PME

IMHO - bad piston choice don't like them ones with rails cut to f*ck

with a window box like G&P & others you want as much complete racks as possible...

https://www.ak2m4.co.uk/internal-parts/pistons/ra-14-5-tooth-piston

or

https://www.ak2m4.co.uk/internal-parts/pistons/cyma-15-tooth-reinforced-piston-piston-head

cyma will req 2nd tooth removing

shs is only half removed

so both will likely need a bit if dremel file work

I would also pay attention to all gears and pinion plus check for bearings for excessive wear

sector is turning but piston is not

piston's teeth look chewed a bit but what about the sector's teeth ???

Did the gun actually cycle ok or did SHS piston - known for binding in some boxes

did the shs piston just refuse to budge on assembly ????

It looks not too bad but the piston most certainly is not being retracted so something is up

just how deep do the sector's teeth mesh into the rack ???

It "sounds" like the pinion isn't high enough - but must be coz nozzle is moving

pay very close attention to sector teeth - well anything with teeth tbh & possible bearing failure

those are my suggestions atm

the piston rack bit I thought was missing was not correct - think they have a bit removed I pointed to

but what on earth is the history with this gun

looks pretty sound - that seems to be a fire-storm mosfeton there too

 

[Adolf Hamster]

Piston has damage to rack guide, possibly allowing rack to shift under stress

either way piston is a goner....

Click to shrink...

good spot, can't beleive i missed that

 

[Delmatron]

Thank you guys.

Dont have a spare piston, are they all the same? As in can we just get a cheap one to see if it fixes the issue?

its almost like there’s no pressure being created by the seal of the piston which could be caused by the broken rack guide you’ve pointed out.

apologies for noob comments or incorrect terminology, I am new to airsofting.

cheers

 

[Sitting Duck]

good spot, can't beleive i missed that

Click to shrink...

actually I mis-diagnosed - oopsie for me - they can come like that

so ignore me coz I'm not 101% certain but still don't like these pistons

think with such little rails on piston they are not very stable flying past that window

I'd still take the other swissed type anyday over these - but only in solid no window boxes

(like say G&G v2 or a V3 box with no window/uninterrupted rails

Thank you guys.

Dont have a spare piston, are they all the same? As in can we just get a cheap one to see if it fixes the issue?

its almost like there’s no pressure being created by the seal of the piston which could be caused by the broken rack guide you’ve pointed out.

apologies for noob comments or incorrect terminology, I am new to airsofting.

cheers

Click to shrink...

piston is not moving at all - you would see the spring twitching and a blur of piston flying back n forth

I mean did the thing work ok ???

did somebody open it up and reassemble it - THEN this problem started

trying to figure out stuff like the piston jumped off the rails just as it closed up

coz it looks a bit wrecked but not like the rack has ripped right out

and gears are turning or tappet/nozzle wouldn't shift

did it just crap out or has somebody been tinkering with this gun

 

[Iceni]

Piston has been crushed. You need a new piston.

The 1st tooth is getting pushed in towards the spring, rather than been pulled back. The swiss cheese job has caused the fault.

 

[Sitting Duck]

Piston has been crushed. You need a new piston.

The 1st tooth is getting pushed in towards the spring, rather than been pulled back. The swiss cheese job has caused the fault.

Click to shrink...

Brilliant spot sir, the white lines on that far right swiss hole indicate the failure

I don't like this SHS piston TT0030  - never have & never will, not enough rails for me

I'm not a great fan of the big hole swiss TT0093 is better but I'd only use say in G&G's

(shs don't bind in G&G's like most others)

I've only swissed a few at that point between rails & rack and tbh the weight gain is f*ck all in the end

in this case 7 or 8 x say 4.5mm holes each side makes little difference to weight in the end under rails

plus I had my reservations about this area

If a reg blue steel rack SHS fits - use that

If not and it binds either make it fit if binding is slight

Or

Use the Cyma piston that pete AK2M4 has started stocking for a tenner with OK POM head

(lose that f*cking heavy alloy weight ffs to save 6gms or so)

A reg std SHS blue full rack is 15.7gms

if you can be ar$ed mild swiss on top only will save you say 15% weight and just go with that

you might get only 10% if very mild swiss on top

you could get 20% saving if going nutz but honestly it is not a great deal to save for messing about

(most of the time is finishing off the holes cleanly etc....)

Even filing off say unused 8 teeth on a DSG I did today wasn't really worth the agro

the full rack weighed 6.75gms, by the time I removed the unused 8 teeth and lowered the 3rd tooth

(2nd tooth already removed btw)

By the end of dremel & filing away them unused teeth it went from 6.75gms to 5.84gms

(ffs thought I'd save a bit more that that)

It was a heavy acm full rack piston with full complete rails which was nearly 19gms

after going full on nutz I got it down to 14gms

this piston doesn't bind where as the shs does - hence me f*cking about with it trying to lose a bit of weight

The shs binds a bit but at 15.7gms with a mild swiss it would have been same if not lighter if I had made it fit

I knew swissing was time consuming, but learnt a bit recently that the savings are quite minimal 

just drop alloy spacer/bearing and you would be hard pushed to save 4 or 5gms from swissing

quite shocked how little was saved from grinding off 8 unused teeth on the DSG rack though

If you are bored, then yeah maybe swiss a shs blue steel rack piston - but it isn't all it is "cracked up" to be

plus the risk of f*cking it all up too....

There is a vid on this bloke doing all the testing bollox which was a bit interesting

he f*cked some up and tried all different patterns and what not....

 

[Hangtight]

The combination of the slightly collapsed rear of the piston and the terrible angle of engagement means the sector gear pick up tooth is completely missing the piston, and is actually passing behind the piston pick up tooth.

If you're using the stock M120 motor on 11.1v and stock gearing (G&P use a 20.2:1 ratio in a lot of their gearboxes) then you shouldn't need a lightened piston.