Materials:
Bandsaw/Hacksaw
4B
Beserker Pump
Spring to fit under the tank firing pin
Hot Glue Gun
Step 1:

Take you stock big blast and unscrew it. If you are minimizing which I recommend do whatever you want to that orange ring on the front, I cut mine with a dremel.
Step 2:

Cut the stock barrel down, and slap whatever coupler you want on. Then for reinforcement, add epoxy putty.

Let that set.
Step 3:

If you can see it, I added a small spring under the firing pin and glued it to the tank and pin. This spring pushes the O-ring up against the tank making pumping easier and much more effective.
Step 4:

Replacing the pump O-ring or whole pump shaft. A Beserker pump shaft is the same size of a 4B pump shaft. It is a little longer but big whoop. If you are using a Orange/White 4B as I am, I suggest either just replacing the O-ring with the Beserker's or the pump handle and put it on the Beserker pump shaft.
Step 5:

Minimization time! I highly recommend this as I said earlier. You may have to cut the hole in the center bigger for your coupler to fit, I used a CPVC one so it required very little effort.
And there you have it! You have repaired a 4B and made it spectacular! My ranges were outstanding and it took about 6-8 pumps for the OPRV to kick in. Before that, it took around 15.
Ranges:
93'
96'
91'
99'
102'
93'
Questions, comments, flames?