First get you supplies:
-Sharpie
-15/32 Brass 1 inch segments
Pipe Cutters
4 9 inch pieces of Cpvc
Epoxy
Hot glue
Plumbers goop
Dremel (Optional)
And of Course a Screw Driver
Supplies:

First start by taking your craking it open, there is a glued tab by the pump so take your saw or dremel and cut open the tab.

After taking apart your turret. Dip it into a pot of boiling hot water and then yank it out with pliers. Then I advise you do Tantum's Airflow mod as it will hep with ranges.
Linky
After doing Tantums, then take you brass like so:

And then Glue it in, epoxy, or whatever the heck you want to do to it in, but make sure that there is 1/2 inch of brass over the lip.
Then take you Cpvc and slide it ontop of the 15/32

Goop them ontop, it should create an airtight seal with minimum deadspaces.
Finish up your other barrels and screw your gun back together.

And your done, Ohh and I suggest gluing the trigger spring tank pin with hot glue as it helps with ranges aswell.
Ranges:With a 1 1/2 dart, 2 copperhead BB's 4 Plugged pumps
97
96
94
103
100
97
76 (Bad Dart)
99
Hope this make it into the directory!