This could be a blamed on a few things... and pictures would be nice, pictures of the barrel and hop up assembly , chamber etc.

First thing its a KWA, they use their own hop up units and are not compatible with most aftermarket ones. So if the guy that checked your gun swapped out the chamber for an incompatible one, you're in for a load of trouble.

Next up, the rubber / barrel thing you're experiencing is normal. KWA also doesnt use standard buckings, so aftermarket ones make your barrel a bit 'too fat' for the chamber. you can work around this tho, not a big issue afaik.

About the hop up itself... only thing I can think of is that the mechanism in the chamber that presses down the arm is faulty somehow. Thats where pictures could come in handy!

 

This could be a blamed on a few things... and pictures would be nice, pictures of the barrel and hop up assembly , chamber etc.

First thing its a KWA, they use their own hop up units and are not compatible with most aftermarket ones. So if the guy that checked your gun swapped out the chamber for an incompatible one, you're in for a load of trouble.

Next up, the rubber / barrel thing you're experiencing is normal. KWA also doesnt use standard buckings, so aftermarket ones make your barrel a bit 'too fat' for the chamber. you can work around this tho, not a big issue afaik.

About the hop up itself... only thing I can think of is that the mechanism in the chamber that presses down the arm is faulty somehow. Thats where pictures could come in handy!

Everything is stock except the bucking which is a gg green. All of the parts function properly but what i did notice is that i can see the bucking inside the barrel without anything pressing down on it.

 

The first thing I would do is simply open up the Hop-up Unit.

I would bet whoever did the bucking install, did so with a straight install approach.
The proper way is to dis-assemble the Hop-up Unit.
My money is on the Nub simply being unseated from its placement holder on the chamber arm.
I always advise to do any bucking/barrel installs with the Hop-up Unit dis-assembled, especially in KWA's.

I have done hundreds of installs with the G&G Green bucking in KWA Hop-up Units specifically.
This I know something about.

 

The first thing I would do is simply open up the Hop-up Unit.

I would bet whoever did the bucking install, did so with a straight install approach.
The proper way is to dis-assemble the Hop-up Unit.
My money is on the Nub simply being unseated from its placement holder on the chamber arm.
I always advise to do any bucking/barrel installs with the Hop-up Unit dis-assembled, especially in KWA's.

I have done hundreds of installs with the G&G Green bucking in KWA Hop-up Units specifically.
This I know something about.

Do you install them using the stock barrel? I switched it out for the stock bucking and it works fine. It didnt seem compatable with the stock barrel.

 

Do you install them using the stock barrel? I switched it out for the stock bucking and it works fine. It didnt seem compatable with the stock barrel.

Yes. I have installed them using the KWA inner barrels as well as my Edgi Barrel, which has a similar OD(Outer Diameter) to the KWA barrel and where the barrel window was cut to KWA specs.
It is more difficult to install the G&G Green with the stock KWA inner barrels vs my MadBull inner barrels and some other after-market inner barrels.
It will fit, it will work, it will be a great performer in your KWA hop-up unit.

Always have a bottle of pure silicone oil to assist with difficult bucking/barrel installs.
I use Team Associated 30wt Shock Oil.
http://www.teamassociated.com/parts/details/5422/

Note:
If you are looking for a great performing bucking, that will work with any weight ammo, and not cause you such difficulty installing in KWA hop-up units specifically, then I highly recommend a Lonex 50 Degree Bucking.
This is the best general purpose drop-in bucking, in my view.

Lonex 50 Degree Bucking:
http://www.clandestineairsoft.com/lonex-c-1_41_43/lonex-50-degree-soft-hopup-bucking-p-259.html