Hi Guys

I have one of these to look at and wondered if anyone amongst you can help out where my knowledge fails me.
I have a Hellcat and was told its down on power but dont worry its intermittent, it is in .177 flavour nd very down on its power but when I looked I found the top hat which is I think the mating surface on the breech is loose to the point of almost falling off. there are 2 allen screws in it which I presume are for locking once it is in the correct allignment.
My problem is I cant find any information or an exploded schematic to allow me to see how its all set up either.
I am wondering if it needs to be against the reciever when cocked and an O ring in there? just face to face which forms a seal when the hammer travels back?
I did try tight back when it was cocked but got a continuous burst of air when I fired it which only stopped once I eased the bolt open gain.

Any pointers that any of you guys can give to point me in the right direction would be gatefully accepted.

Many thanks in advance Martini