By doing this mod, you will increase the power & distance of each shot. The only down-side is that you have pull the slide back hard & sharp.
Step 1: Un-Screw
Step 2: What you're doing
Step 3: How much to add
*EDIT* A lot of people are saying that they used pennies, and the they worked fine. So just whatever floats your boat, i guess.
Step 4: Experiment
Step 5: Finishing Up
Troubleshooting: If you can't pull back the slide, then you might not have the trigger spring in place