This is easy just take it apart piece by piece, starting with the barrel then the fore grip. Make sure when you pop the main chassis open you know where every thing goes. You should have a manual anyway showing where everything goes. Either place around 2 inches of spacers in the piston tube in front of the spring or add a spacer and another spring from an airsoft pistol, most suitably from a Marui hop-up. On my Dong San Spas-12, the piston was a bit small for the outer tube and air was pushed backward out of the piston, not just out the front. Some electrical tape warmed on a radiator and wrapped around the tube very tightly will solve this. Add some silicon grease or spray. Put it back together and your sorted for more power. If your gun f#cks up though, it ain't my fault. But this does work.

WARNING: Neither X-ring nor anyone else assumes any responsibility for anything you do with airsoft models. Anything you do with airsoft is at your own risk!