Powertube gas line?

Tippmann 98 Custom Pro Platinum
Took the marker apart recently for maintenance and while I was monkeying around the powertube popped out.  At first glance it looks like the airline is supposed to thread into the powertube, but it doesn't look like it came that way out of the box and I can't seem to screw the airline into the powertube..  The airline is still attached to the shell and the whole powertube popped out of the gun.

 Does the power tube really just sit in there? How does that not leak???? I haven't gassed my gun up, but something just doesn't seem right. I had a little bit of trouble lineing the powertube up with the gas line but maybe I should have pulled the gas line off of the shell and put the powertube and the gas line together separately (is that possible?)..   

My powertube is still fully assembled, I know enough not to mess with it but I need to put it back in place.

I've seen on youtube a couple videos where it looks like the powertube is indeed threaded into the gas line.. I can't seem to be able to make that happen as it looks like the gas line just sits on there like a cup in a saucer...   I don't know if the gas line is broken off inside the powertube or if it's supposed to be that way?? What do I do? Please help, thanks..