Low fps could it be cylinder related?

[Pollynator_bravo2]

The SHS nozzles I bought a while ago were supposed to be 21.3 but they turned out to be 21.5 and change..

Length also depends on the hop unit, hop rubber and inner barrel, some combinations love short nozzles, others want longer.

For example the Maxx TE hop I have in my pdw says it wants 21.25mm tops but ran fine on the aforementioned 21.5mm shs nozzle for a while.

So the inner barrel is 360mm

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[Lozart]

When you say timing do you mean when the nozzle moves forward and locates the bb into the feed lips before the piston sends the air down? Sorry if that’s a stupid question 

also where should the nozzle

locate to when it enters the hop again?

I am not getting any miss feeding when the gun fires bbs fly so I think the retraction etc is ok

So the inner barrel is 360mm

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Timing does indeed mean the cycle of retracting the nozzle to allow the bb into the hop unit, then allowing it forward to seat the BB into the hop before the piston comes forward. If you're not getting a feeding issue that should be OK but if the nozzle isn't actually seating on the feed lips of the hop rubber properly you may be getting an air leak.

The chamfered tip of the nozzle should seal into the end of the hop rubber (the feed lip if you will). An easy test is to reassemble the gun, turn it upside down and place a small piece of paper over the feed tube. When you fire the gun the paper should move only minimally, if it blows off then there is air escaping down the feed tube.

Also - it may be the camera angle but your barrel doen't look straight in your hop unit - it may need twisting slightly to line it up.

 

[Pollynator_bravo2]

Timing does indeed mean the cycle of retracting the nozzle to allow the bb into the hop unit, then allowing it forward to seat the BB into the hop before the piston comes forward. If you're not getting a feeding issue that should be OK but if the nozzle isn't actually seating on the feed lips of the hop rubber properly you may be getting an air leak.

The chamfered tip of the nozzle should seal into the end of the hop rubber (the feed lip if you will). An easy test is to reassemble the gun, turn it upside down and place a small piece of paper over the feed tube. When you fire the gun the paper should move only minimally, if it blows off then there is air escaping down the feed tube.

Also - it may be the camera angle but your barrel doen't look straight in your hop unit - it may need twisting slightly to line it up.

Awesome thanks I’ll try this. 
 

if there is a leak does that mean I should fit a delay chip or slightly longer nozzle?

 

[Lozart]

Awesome thanks I’ll try this. 
 

if there is a leak does that mean I should fit a delay chip or slightly longer nozzle?

If there's a leak it's going to be most likely the nozzle length.

 

[ak2m4]

@Pollynator_bravo2 clean that inner barrel and wash that rubber 

 

[Rogerborg]

@Pollynator_bravo2 clean that inner barrel and wash that rubber 

We have to maintain our toys?

 

[Dan Robinson]

We have to maintain our toys?

Never was a character so true to life.

[father of a 15 year old]

 

[Pollynator_bravo2]

@Pollynator_bravo2 clean that inner barrel and wash that rubber 

Yeah fair point. Not done anything to it since I brought it off a seller. I think it was thrown together with bits from the Airsoft fair

 

[Pollynator_bravo2]

Timing does indeed mean the cycle of retracting the nozzle to allow the bb into the hop unit, then allowing it forward to seat the BB into the hop before the piston comes forward. If you're not getting a feeding issue that should be OK but if the nozzle isn't actually seating on the feed lips of the hop rubber properly you may be getting an air leak.

The chamfered tip of the nozzle should seal into the end of the hop rubber (the feed lip if you will). An easy test is to reassemble the gun, turn it upside down and place a small piece of paper over the feed tube. When you fire the gun the paper should move only minimally, if it blows off then there is air escaping down the feed tube.

Also - it may be the camera angle but your barrel doen't look straight in your hop unit - it may need twisting slightly to line it up.

So the paper moved a fair bit so I’m guessing air is escaping ?‍


IMG_3676.mov

 

 

[Lozart]

So the paper moved a fair bit so I’m guessing air is escaping ?‍

IMG_3676.mov 10.52 MB · 8 downloads  

We have a winner!

Tip of the nozzle isn't sealing with the rubber.

 

[Colin Allen]

So the paper moved a fair bit so I’m guessing air is escaping ?‍


IMG_3676.mov 10.52 MB · 10 downloads

The nozzle is not fully engaging with the hop rubber lips.  Is the hop unit pushed fully back against the gearbox?  If it isn't, use some O rings in front of it to push it back.  If it is, try longer nozzles or get a variable nozzle.

 

[Pollynator_bravo2]

The nozzle is not fully engaging with the hop rubber lips.  Is the hop unit pushed fully back against the gearbox?  If it isn't, use some O rings in front of it to push it back.  If it is, try longer nozzles or get a variable nozzle.

It’s a weird one as I grabbed the old gear box that came out of it and serviced it fully. When I opened it up the tappet plate looked different. It has a moon shape on the tail end and there is a delay chip however the nozzle is shorter than what I had in the eon gb. When I fitted it all back together (with a clean inner barrel and bucking) I got 335 fps and 1.28j (no hop applied) ?‍??‍

I guess this is an easier problem to fix the the latter lol

images are of the gb that came with the gun when I brought it 2nd hand

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[Colin Allen]

It’s a weird one as I grabbed the old gear box that came out of it and serviced it fully. When I opened it up the tappet plate looked different. It has a moon shape on the tail end and there is a delay chip however the nozzle is shorter than what I had in the eon gb. When I fitted it all back together (with a clean inner barrel and bucking) I got 335 fps and 1.28j (no hop applied) ?‍??‍

I guess this is an easier problem to fix the the latter lol

images are of the gb that came with the gun when I brought it 2nd hand

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That seems to be the best way forward.  I have never seen a tappet plate like that before.

 

[Lozart]

It’s a weird one as I grabbed the old gear box that came out of it and serviced it fully. When I opened it up the tappet plate looked different. It has a moon shape on the tail end and there is a delay chip however the nozzle is shorter than what I had in the eon gb. When I fitted it all back together (with a clean inner barrel and bucking) I got 335 fps and 1.28j (no hop applied) ?‍??‍

I guess this is an easier problem to fix the the latter lol

images are of the gb that came with the gun when I brought it 2nd hand

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Wow, that is OLD!

The different design of tappet plate would certainly account for what you're seeing. The fix will still be a longer nozzle though as you can't get tappet plates like that any more.

 

[ak2m4]

Wow, that is OLD!

 Jurassic Army.  Look at the size of the vent holes in the piston head.  Length of the cylinder head shaft looks quite long as well.  Looks all nice and clean, cheap to fix up and run

 

[Lozart]

 Jurassic Army.  Look at the size of the vent holes in the piston head.  Length of the cylinder head shaft looks quite long as well.  Looks all nice and clean, cheap to fix up and run

I was just thinking that, it's in bloody good nick for its age!

 

[Colin Allen]

Wow, that is OLD!

The different design of tappet plate would certainly account for what you're seeing. The fix will still be a longer nozzle though as you can't get tappet plates like that any more.

He could try fitting a standard tappet plate and seeing how that goes; it might still need a different nozzle.

 

[Lozart]

He could try fitting a standard tappet plate and seeing how that goes; it might still need a different nozzle.

Absolutely, other than being drier than a nuns fanny it seems to be in pretty good nick.

 

[Colin Allen]

Absolutely, other than being drier than a nuns fanny it seems to be in pretty good nick.

It is surprising how good some gearboxes look after a long period.  I opened up the lad’s blowback G&G AKM on Sunday to deal with a low power issue, after it had not been opened for many years.  Apart from a worn piston head O ring, it was pretty much perfect.

it was still a bugger to do due to the stupid pneumatic blowback system.

 

[Pollynator_bravo2]

Absolutely, other than being drier than a nuns fanny it seems to be in pretty good nick.

That was before being cleaned and lubed up. Was wetter than Gemma Collins mouth in greggs 

It is surprising how good some gearboxes look after a long period.  I opened up the lad’s blowback G&G AKM on Sunday to deal with a low power issue, after it had not been opened for many years.  Apart from a worn piston head O ring, it was pretty much perfect.

it was still a bugger to do due to the stupid pneumatic blowback system.

What’s the correct O ring size for the piston and cylinder head ?