This is the easier way to mod this gun. First step as always, take it apart. Lots of screws, keep track of them, don't forget the metal bit on the handle.

Step 1: The Barrel

Inside the barrel you'll find a barrel post. Get some needle nose pliers and twist it out.

Step 2: Restrictor

Here's the part you want to remove. Now instead of un-gluing the barrel or twisting scissors on it, possibly ruining it, just take a drill with a 3/8" bit, and drill it out. Use a good amount of force, be careful as the drill might get stuck on the spring holding the restrictor. Stop every once in a while and clear out the plastic shavings.