FAMAS compression issue Massive FPS loss

[Goge]

I have a been tinkering with my FAMAS and finally getting a chrono I tested it and I am getting only 190 to 230 fps. It currently has in it:
Guarder 550mm 6.02mm inner barrel
Element Bearing Vortex Metal Spring Guide for Ver. 3 screwed in place.
Element 300% Torque Up Helical Gear Set
Systema Energy Piston
Element POM Bearing Piston Head
Sorbo Pad
Stock Cylinder / Cylinder Head / Nozzel
Guarder SP100 spring (should be 330-350fps)

Because of the issues in this FAMAS Cylinder requires piston short stroking thread, the piston and gears are short stroked.'

What I think may be an issue and I'm asking the pros if this is plaussable is:

Could the barrel now be too long for the short stroked and sorbo padded cylinder which was already small to begin with?

[Goge]

update:
I've swapped the short-stroked piston and gears back to stock and removed the sorbo and I am still getting the FPS drain and occasional miss-fire.

I used the flashlight method to check if the air nozzel was sealing with the hop up and it wasn't. I used this Tappet Plate Mod to make a better seal. This gave me a 20-30fps rise but it is still far too low.

Anyone at all have any ideas?

[Shell Shock]

hmm.. sounds like a problem i faced with my old mp5. if so, my solution is simple and highly effective. all you need is some Teflon tape (used in plumbing and air systems.. see where im going with this?)

1- disassemble AEG until you have full access to the following: hopup, gearbox and inner barrel

2- remove the inner barrel from the hop up and wrap a layer or two of teflon tape around where the inner barrel and the hop up meets (not where the "nub" goes through though)

3- open your mechbox and put one or two wraps of Teflon tape around the piston head.

you must make sure you do this very neatly, or in a month you will have to clear your inner barrel of Teflon tape and start again.

[Ninja_En_Short]

What ??? You can still close the GB properly like that ?

Put tape inside the mechbox is a very serious no go for me. Only one thing for air seal : silicon seal. just go at any Canadian Tire and take some, I use a transparent one normally made for doors (don't put that on your bare finger).
Put some of that around the rubber seal of your cylinder head, don't hesitate to make a massive one, when you put back in place in the cylinder, just remove a the overflow but leave a little bit and stretch it a bit on the cylinder to make a nice seal.
It will do, in my opinion, a better job that any tape out there.

For the piton use some white lithium grease, it's getting cold and regular grease have a tendency to make small frozen bit in the GB... and the gears hate rocks. Put som on the piston rails, the teeth and around the rubber seal of the piston head.

If you still have problem, try to look at the seal between the nozzle and hop up rubber.

DO NOT PUT tape on the hop up rubber and inner barrel : if dismounting needed, you take the risk of tearing it ! Plus it's going to be a pain to put in hop up block.
You can however put a little lithium grease or silicon oil on the barrel before putting the rubber on : when drying it's going to make a "semi solid" seal (I don't have a better name for it). Be sure the rubber is perfectly in place : the barrel must go all the way in an be in contact with the bottom.

What is the brand of the FAMAS actually ? It may give leads on where to look.

[Shell Shock]

Originally Posted by Ninja_En_Short

What ??? You can still close the GB properly like that ?

Put tape inside the mechbox is a very serious no go for me. Only one thing for air seal : silicon seal. just go at any Canadian Tire and take some, I use a transparent one normally made for doors (don't put that on your bare finger).
Put some of that around the rubber seal of your cylinder head, don't hesitate to make a massive one, when you put back in place in the cylinder, just remove a the overflow but leave a little bit and stretch it a bit on the cylinder to make a nice seal.
It will do, in my opinion, a better job that any tape out there.

For the piton use some white lithium grease, it's getting cold and regular grease have a tendency to make small frozen bit in the GB... and the gears hate rocks. Put som on the piston rails, the teeth and around the rubber seal of the piston head.

If you still have problem, try to look at the seal between the nozzle and hop up rubber.



DO NOT PUT tape on the hop up rubber and inner barrel : if dismounting needed, you take the risk of tearing it ! Plus it's going to be a pain to put in hop up block.
You can however put a little lithium grease or silicon oil on the barrel before putting the rubber on : when drying it's going to make a "semi solid" seal (I don't have a better name for it). Be sure the rubber is perfectly in place : the barrel must go all the way in an be in contact with the bottom.

What is the brand of the FAMAS actually ? It may give leads on where to look.

its not sticky tape. its used in pneumatic systems and hydraulics. and the total of two layers of this stuff only adds an additional .1mm or so, not nearly enough to make it really difficult to do a full disassemble.

Originally Posted by CDN_Stalker

It's an old trick to do on sniper rifles and some AEGs. Won't damage anything, but you might find the hop up/inner barrel difficult to reinstall due to the added bulk of the tape. Trail and error really, but it only works once. If you take it apart in the future, you'll have to apply new tape.

stolen from a thread early on in the year. i suggested this method due to the fact that it sounds like he has a serious rubber problem, be it gap, or cracks in the rubber. it is not touching the nub.

[Goge]

So the Teflon goes around the barrel before I install the barrel into the hop up unit? Won't that mess with the little grove for alignment on the barrel? If I'm reading this right it seems like this is the fabled "teflon mod". I have assignments and exams coming up so I won't be able to try this until mid December when the semester is over but I will definitely give it a shot.

Thanks

[Shell Shock]

ok, so i realized my image sucked. so here is a better image. its not my image, but it is better then any pic i could have provided. the white stuff is the tape. this person put a bit too much. and it should not be covering the nub or the hole in the top of the barrel.

best regards
shell shock