Loss of about 200fps

[LazzurusMan]

So I recently put a new gearbox shell and nozzle in my Ares mutant. Did everything as I normally would, went to test it and I went from 345fps consistent to 140 and less.

 

My only guesses are my spring somehow wasn't in properly (don't know how that'd happen or what it's catch on), the new nozzle is worse than the stock one, or as I've put it together something hasn't gone together right. 

I'm almost at the point of giving up, I've already put too much money into this damn thing after two gears broke after a few games (spread over a year and a half, so no warranty). 

[Leo Greer]

Is the gearbox another Ares? If it’s not, chances are you have a misaligned gearbox, as boxes are absolutely not made to spec, especially Ares.

 

Get an adjustable nozzle to check for nozzle length issues.

 

Make sure your cylinder sits tight in the shell.

 

Is this happening on full auto, semi, or both? What’s the ROF?

[LazzurusMan]

Rof is high 20s, I guess it could be slowing the BBS down as the piston draws back, even in semi. 

 

Same gearbox, just new. And it's the same FPS on both semi and auto. Could it be the nozzle is too long? I think it was a few mil longer. 

[Rogerborg]

I'd expect to see that from a shorter nozzle. Longer tends to give feeding issues. Or it might be narrower externally and just not sealing in the bucking.

 

Then again, I wouldn't assume that a new / "new" gearbox has good internal airseal without checking it. Even if it was good at the factory, it could have been drying out in shipping and shelves since forever ago.

 

The very first thing I'd do is spooge some silicone liquid or spray up the nozzle into the cylinder, let it soak in, then cycle it until it's blowing clear.

 

 

[LazzurusMan]

So, when I installed the replacement gearbox shell, I rebuilt the whole thing. It should have been just as good as it was before the replacement.

 

However, I've just taken it apart again to check compression, and my piston head is NOT making a good seal. I hold a finger over the nozzle and compress the piston, and I can hear air escaping past the piston head. Iring looks ok, it VERY well lubricated. I have no idea why it's doing this. Anyone got any ideas??

[ak2m4]

2 hours ago, LazzurusMan said:

However, I've just taken it apart again to check compression, and my piston head is NOT making a good seal. I hold a finger over the nozzle and compress the piston, and I can hear air escaping past the piston head. Iring looks ok, it VERY well lubricated. I have no idea why it's doing this. Anyone got any ideas??

 

Sounds to me like either the o-ring on the piston head is too small for the cylinder or the vents are clogged up stopping the oring from being pushed out.

[LazzurusMan]

6 minutes ago, ak2m4 said:

 

Sounds to me like either the o-ring on the piston head is too small for the cylinder or the vents are clogged up stopping the oring from being pushed out.

Iring seems to be fine, I get good compression when I tested, after clearing out the vents. However, I did discover after putting it back together for another fps test that some shots I could see the air hit my duvet (I don't really have anywhere better to test) then I would hear the bb slowly roll down the barrel before falling out. Could the nozzle being too long be causing any kind of feeding issue that would result in this? Or perhaps it's a problem with the bucking?

Could precocking be causing issues? All I did was move the magnet that the efcs uses into a different position based on what others have said to do to precock it.

[Tackle]

A blast of air & then the BB rolls out ??????, that's weird AF. 

Definitely sounds like a feeding issue, maybe try some different mags in case the one your using is a bit "sticky" & not feeding fast enough for your high rps ? 

Don't know nowt about efcs, but if it's simple to return it to its default position I'd do that too ? 

[Leo Greer]

Do you know the old o-ring stretch trick?

 

Your airseal would have to be freaking horrendous to lose 200 FPS at the piston head/cylinder junction. For reference, I’ve done some work on certain Lancer Craptical guns that didn’t even have airseal between the head and cylinder, and still got over 300 FPS (supposed to shoot 375). I’m not kidding here.

 

When your nozzle is too long it can lose you FPS consistency, accuracy, feeding… usually not more than 10-12 FPS at max though.

 

My best bet is that you’re getting drag on your tappet plate/nozzle, if your tappet timing is off because of drag, it can easily cause that much FPS loss. Check for any friction between the GB shell and the tappet and the nozzle and the nozzle tube. Make sure you check with the GB screwed together tightly.

 

Oh, and also check and make your nozzle is at the right angle—if it’s angled it can do that.

 

Mag issues are a decent guess, methinks, but it’s been a while since I’ve seen mags do that—I’ve had feeding issues (darn you Lancer midcaps), and sometimes this causes FPS drop as well, but I’ve never seen 200.

[LazzurusMan]

Ok, so I just did the tissue/paper test. That came flying out when I fired it, so I'm losing all my compression at the nozzle/bucking seal. Now in theory the new nozzle, it being longer, should give a better seal. But I'm guessing it might be a little thinner. either that or my bucking lips are shagged.

[Leo Greer]

Maxx adjustable nozzle = your best friend.

[LazzurusMan]

This is probably the culprit, and the other bucking I used to test is an old knackered guarder black, that everytime I tried to install would slide further up the barrel meaning the lips wouldn't meet the nozzle. Im going to do armaments today so I'll put it all back together, bring the rifle and my chroni and pick up a fresh bucking. That's if anyone else thinks I could lose 200 fps just from the nozzle not reaching the bucking?

 

 

[Rogerborg]

Yup, that'll do it.  The air is going to take the path of least resistance, and if that's down the feed tube, that's where it's going.

 

If the bucking is that knackered, it may also be blowing between the bucking and the outside of the barrel, although the Maple Leaf ridges are meant to (and seem to) give a better seal.  That's where PTFE tape might help though - I put it on for ritual purposes, and then silicone lube the outside of the bucking / inside of the hop to help it slide in.

 

Also, does your hop unit have a spring pushing it back against the gearbox?  Is it still springy?

 

[LazzurusMan]

21 minutes ago, Rogerborg said:

Yup, that'll do it.  The air is going to take the path of least resistance, and if that's down the feed tube, that's where it's going.

 

If the bucking is that knackered, it may also be blowing between the bucking and the outside of the barrel, although the Maple Leaf ridges are meant to (and seem to) give a better seal.  That's where PTFE tape might help though - I put it on for ritual purposes, and then silicone lube the outside of the bucking / inside of the hop to help it slide in.

 

Also, does your hop unit have a spring pushing it back against the gearbox?  Is it still springy?

 

Oh it's tight against the gearbox. The amoeba mutants have a spring in the outer barrel that pushed the proprietary hop unit tight, then it's also held in place with a couple of hex bolts.

 

I've gone through everything except putting a new maple leaf bucking in, so hopefully when I pick up a new super macron today it should be back up near 350. Might be a little over as the new nozzle, which has never been tested with a decent bucking, has orings and the stock one didn't. That'll be an easy fix If it is, I'll just rip the spring out and take a little more off it. 

 

 

Cheers everyone, hopefully I won't be posting I'm this thread again 🤣🤣

[LazzurusMan]

Ok, so I put the new bucking in, and it wouldn't feed at all with the aftermarket nozzle I put in. (Didn't lose my range time though as I also bought a new areas l85a3 as an early birthday gift to me).

 

Seeing as the new nozzle is only a millimeter or two longer, would that really stop it from feeding at all?

[ak2m4]

2 minutes ago, LazzurusMan said:

Seeing as the new nozzle is only a millimeter or two longer, would that really stop it from feeding at all?

 

yes, even something 0.5mm can cause issues.  what's the length of the stock and new nozzle?  have you tried fitting the old nozzle?

[Rogerborg]

7 minutes ago, LazzurusMan said:

Seeing as the new nozzle is only a millimeter or two longer, would that really stop it from feeding at all?

 

Yes. Fractions of a mm can do it. Maple leaf rubbers have longer lips which can also contribute - I've had to trim a tiny sliver off of the bottom of a lip before.

 

If you're sure that it's nozzle length, you can file it down, just don't create any burrs or sharp edges.

 

Airsoft compatibility, eh?  It's a wonder any of it ever works at all.

[ak2m4]

To give you an idea Maple Leaf lips are 1.9mm long, whereas most are around 1.2mm (I think, need to check, got all measurements round here somewhere).

 

Also the aperture of the Maple Leaf is wide enough to park a bus, ok so wide enough to let a BB fall through without any encouragement, whereas standard buckings a BB will sit on top of the whole waiting for a little tap to proceed.

Ditch the Maple Leaf for now and try just a regular bucking for now.

[LazzurusMan]

1 hour ago, ak2m4 said:

To give you an idea Maple Leaf lips are 1.9mm long, whereas most are around 1.2mm (I think, need to check, got all measurements round here somewhere).

 

Also the aperture of the Maple Leaf is wide enough to park a bus, ok so wide enough to let a BB fall through without any encouragement, whereas standard buckings a BB will sit on top of the whole waiting for a little tap to proceed.

Ditch the Maple Leaf for now and try just a regular bucking for now.

Unfortunately the maple leaf bucking is all I have. I've also had no issues with them before (except for the shagged one, which probably happened when fitting it knowing my clumsy hands).

 

I don't know the length of the ares nozzle as I don't have any calipers to measure with, but the replacement is listed as 21.4mm. it's the rocket double oring nozzle. I'll wack the original nozzle in and see what happens. It had perfect fps before I changed the nozzle, but the stock one is plastic and I wanted to eliminate that as a weakpoint.

[LazzurusMan]

Ok, just been thrown a curve ball here.

 

My nozzle doesn't go all the way back before coming back forwards. It looks like the tappet plate itself bends upwards towards the piston and doesn't go back all the way. It's almost like the tappet spring is too strong. Possibly a stupid question, but is the nozzle supposed to go back as far as the cylinder head?

Edited January 28, 2023 by LazzurusMan

[LazzurusMan]

Ok. I'm at my wit's end.

 

 

Stock nozzle refitted, brand new super macron bucking with omega nub, barrel polished, piston, piston head, cylinder, cylinder head all checked for compression and it's all good. 

 

I'm still only getting 140 FPS on .2s, and using the paper test the paper still flies out of the magwell. The only thing I can think of is the stock nozzle not sealing with the hob bucking well enough, which means taking it all apart and fitting the new nozzle. Again.

 

Anyone got any other theories?

[LazzurusMan]

So, in case anyone else has this issue at any point, I'll explain what the issue/s was.

 

1. Short troking and precocking without adjusting the tappet timing. Nozzle was coming forward just after the piston. Big loss of fps there.

 

2. Shagged bucking. Speaks for itself.

 

3. Crap mags. I kept getting anything from 160fps to 330 with the wind up mags I have that don't fit great but usually still feed. I switched to a poly midcap that fit better, and I went back up to a relatively consistent 343-345.

 

 

Thank you again everyone for your help, now I can focus on starting a dmr build 🤣

[Rogerborg]

Ah, I wonder if that's BBs in the feed tube pushing the nozzle up too hard.  Luke at Negative put a video up recently showing the difference between a wobbly nozzle and a firm one (fnar) and suggested very slightly flaring the end of the cylinder head tube (inside the nozzle) using a swage to minimise the slop.