Why does it have to be unthreaded just curious?

I use this:
http://www.genuineinnovations.com/bi...=1&prodid=1000
Its the airchuck SL. It is very very simple as far as CO2 goes. I can't say it works as well as some trigger set up, but it does do great job and its very quick. It's also teeny so I don't need to have a huge seat bag.

Edit:I see why you cant have threaded, my bad. If you ever do go this route though I recommend it.