NYC Airsoft

so I run a somewhat modified G&G CQBR, and although I love it to death, the barrel threading on my particular weapon is just terrible. on the plus side, the Whole outer barrel assembly is so easy to swap, I've decided to just buy a new short barrel and permanently modify the old one into a standard length barrel for slightly better range when needed.
I've decided to do this using the following parts:
One of those common 14mm CCW JG/Matrix M4 outer barrel extensions
a new flash hider
a few washers to hold the flash hider in place on the end of the barrel extension

now my question is, how would you guys recommend permanently affixing the longer barrel extension to the barrel of my rifle? Weld it? Epoxy? plumbers cement?
any help would be appreciated.

Why do you want to make it permanent? Because of the thread?

Try some loctite thread sealer. It should help lock it in better, blue is the mild stuff than can be easily removed if needed, red is the tougher stuff that will need heat if you want to remove it.

I want to make it permanent because the threading is pretty shot, and also so I could have two seperate barrels for my rifle: a long and a short. Instead of buying a whole new long outer barrel, I figured I'd just add on to the current one. And then I could buy a new short barrel whenever.

14mm x 1.0 HS 1-1/2 Inch Outside Diameter LEFT HAND Die
http://www.amazon.com/gp/product/B0007K ... UTF8&psc=1

Worked for me on a barrel someone gave me with screwed up threads on the end. Of course i got the Right handed Die, Right & Left Handed tap as well.