How to take the PGP Apart

Step 1: Gather the tools you will need
Allen wrenches: 5/64″, 3/32″ (preferably a complete set)
Channel-locks or a small vice, vice grips, or similar
piece of leather or inner tube rubber or similar
couple of empty 12-gram cartridges

Step 2: Make sure your PGP is completely unloaded.
Remove the 12-gram cartridge if present
Remove all paintballs.

Step 3: Remove Pump Handle
Pull the pump rod from the bolt rotate pump rod so it won’t scratch the marker and slide pump handle forward and off of PGP

Step 4: Remove the Bolt
Cock the gun, put it the safety on. Rotate the bolt clockwise at close bolt position, then pull the bolt out.

Step 5: Remove Hammer
Remove the rear grip frame screw using the 3/32″ Allen wrench Remove Velocity Adjuster, mainspring, and hammer. You may need to pull the trigger for the hammer to fall free from the PGP.

Step 6: Remove Grip Frame
Remove front grip frame screw while holding grip frame to gun body. This is to prevent losing the safety spring and BB. While holding gun upright, carefully lift gun body off of grip frame. The safety ball and spring should still be in place. Set grip frame aside. Further disassembly should be unnecessary. 

Step 7: Remove valve
The valve assembly may now be pushed out the REAR of the gun. Use two empty 12 grams, but use whatever is convenient. Be careful not to use something pointed, however, as this could damage the 12 gram seal.

Step 8: Disassemble Valve
Don’t do it unless you know what you are doing! If you sure you want to do this, see http://pgpog.org/apart.html for more details.

Or simplely check out this Disassembly Walkthrough.
http://www.pbase.com/the_kampfer/disassembly_walkthrough