Okay. Here are the pics.
This is the project gun before the operation
This is the hose, the torniquet rubber.
This is the barrel with the hole/serration made with a file.
This is the barrel inserted into the hose
This is the clamp with screw
This is the assembled barrel with hop-up
And another view
This is the finished gun. Note the hop up screw made accessible from the top.
There ! I hope enough guys do this to their teka-teka's and we can play using those gear !