Cocking tube upgrade on "3rd gen" GSG 522

[evilevilforces]

Ok, so I have what I've seen called a 3rd gen gsg522 and I'm trying to install a gsg5 cocking tube and front site.  I've watched the video online on how to disassemble the rifle and take the cocking tube off but mine is different than the one shown.

Instead of 3 screws holding the cocking tube and barrel there are 4.  I take the top two off, loosen the bottom two and try to remove the cocking tube and it will only budge about 1 millimeter and stops. 

I then tried to disassemble the body of the rifle to see if that's how it needs to go now and it is impossible to take it apart apparently if the cocking tube is still installed.  It won't pry apart at the barrel.

I can't see anything that is holding the cocking tube on or holding the body of the rifle together and it's pretty infuriating.

How the hell do you do this?  What am I missing?

[Kilibreaux]

Sorry I came late to this post...been in a land far away.

The cocking tube must slide forward a small amount to allow the receiver halves to separate.

In case you haven't already solved this...when you reassemble you can use a hot glue gun to "tack" the upper receiver insert (metal if you're doing the GSG-5 retro fit) to one receiver side and this will avoid needing that third hand.