Thunder maul - Dragon Low FPS miss feeding

[ScooterVauto]

Hello folks
== History == Bought from a bone yard shooting 19RPS @ 140 FPS.
SB Black Version 2 JG mechbox.
rebuilt mechbox and replace stock wore parts with TM psiton head, SystemA
Cylinder head, Guarder Tappet, TM nozzel, Dboys Cylinder (ported) TM Spring Guide & PDI 130% Pro Spring.

I matched the dboys ported Cylinder with the 6 inch inner and outer barrel it
came with, so to that the cylinder matches the barrel lenght.
The Cylinder that was in it was chorme plated, the piston head path inside was wore to the brass -- THE ENTIRE piston head path.
Many many BBs have been fire prior to this purchase.

Assembled it and the speed came up to 216 FPS.
Tested the mech box in another M4 through a SystemA hopup, Guarder Black rubber (normal Nub) & a 455mm Promethus TBB the Speed was
7 out of 10 378, 2x 379 & 1x 380 Dame consistance and Shooting fast.

MechBox Checks out For sure.

the upper and lower are TM clones with a 2 piece hopup
I have gone so far as to remove the stock hopup upper assembly and replaced it with a TM from my M733, and my 455mm Promethus TBB
and it still shoots under 200 FPS.

The Stock Nozzel was 1mm shorter then a regular m4 nozzel so i assumed it was wear but as its a TM clone, the proper Nozzel should be an M4 nozzel
so i replace it with the one from my M733..
Dam i am stumped...

Please any help would be greatly appreciated.

[Styrak]

Replace the hopup rubber? Perhaps it isn't making a seal. That can happen if the end of the rubber is damaged/chewed up.

[ScooterVauto]

the stock one was black and almost unable to remove from the barrel,
i am currently using a G&G or G&P green one.
I'll try a Guarder Black or a system 60% the next time i open her up
(ok its opened up the next time I feel like falling on my face again hahaha)
Thanks Styrak, I'll let you know in a few

[Styrak]

Green would be G&G. If you've already replaced it, it probably wouldn't be that.
You could try a different one though.
Does the cylinder/head/piston head seal completely? Have you tried a compression test?

[ScooterVauto]

i tested the rebuilt mechbox in a different M4,
That rifle has a systema Hopup assembly, Guarder black through a Promethus 455mm
in there it shoots constant 378,
So i ruled out the mechbox internals.

[Styrak]

Then its the airseal somewhere, that's a fact.

Hopup or rubber or nozzle, or a combination of all three.

[ScooterVauto]

so are you ready for this,
Took the stock hopup, with the dboys barrel and the green hopup rubber,
HELD it to the Front on the assembled bottom half and
it shoots 350???
put it in the upper and put them together 216??
Itslike the upper hopup assembly is not sealing against the lower bb chase thus a seal leak..

[Styrak]

No it sounds like the nozzle isn't sealing with the hopup.

The upper and lower hopup halves don't have a "seal".
Is the spring that's on the top of the hopup missing perchance?

[ScooterVauto]

spring is there Yes sir and the tm hop up moves freely in and out,
the stock one moves freely to a point (a little past half way on) then a little push
and it locks all the way in

[Styrak]

So it's the seal like i said "Hopup or rubber or nozzle, or a combination of all three."

[ScooterVauto]

well I'll try a few things,
With 2 different hop ups, What should be a Proper m4 nozzle (from a TM m733 with the same style hopup set up) hell and the hopup assembly ,
Im going to try putting a Guarder black in the Stock hopup with the Dboys barrel
and a Systema black in the TM hopup with my 455 Promy.
I'll get back in a bit
this will take a few hahaha

[Styrak]

Yeah if you keep swapping parts you'll eventually see what's wrong.
Swap one part at a time or you'll never figure it out

[ScooterVauto]

thats what i figure.
the stock setup will have 1 change a different hopup rubber
and the tm setup is..well. and entirely different setup.
if both suck butt. I'll take the mechbox out of my M733 and drop
that into the Mauls upper and lower with the TM setup and see what happens then.

If that doesnt work.
It must be GOD HATES ME hahahaha
back soon, was food time, now work time

[ScooterVauto]

so same low fps with either set up.BUUUT
If i hold the inner barrel back against the mechbox (with either barrel a little sticks out the front of the outer)
But if i pull it back (not that i actually feel it move) the FPS JUMPS.
Tomorrow i am going to try a different mechbox in the maul and see what happens.
Maybe I need a longer nozzel? Only thing left. Or a strong spring to hold the hopup back hahah

[IggysPiggy]

do you have the lower body pin inserted while testing? if there is any misalignment in mech box to hop up the nozzle will not move freely enough to seal against the rubber before the piston is released. also you said it is a two piece hopup. check the lower feeder to make sure it is securely screwed down and not shifted either up or down or tweak side to side ( ie: one screw tighter then the other. although you said when you changed the upper hopup piece it solved the issue). Another test is to take the original hopup upper you were using and switch out the six inch barrel with your longer tbb WITH the old rubber, insert test if it shoots high then its a upper hopup issue if it shoots consistant id start looking at that six inch barrel. as well when you pulled the barrel and rubber were you careful about reinserting the hopup nub, if it went in side ways it could be putting to much pressure.

just some more ideas for you,

Cheers, Jesse