Step 2: Upgrading: Part 1
The first is to upgrade that big fat spring. It's found in the big orange cylinder. Right now it's about 2 inches in diameter and around 6 inches long. You have 3 choices. You can add a second spring, you can stretch it, or you can use a spring from an AR-15 assault rifle.
If you decide to stretch the spring, make sure you know what you're doing. Spring manufacturers know what they're doing. When you grab it and stretch it, it will work well for a few times before it gets worse than how it used to be. My bet would be that if you have to do this, you can stretch it, hit it with a blowtorch, and let it air-cool.
A second spring doesn't seem to help, unless it fits perfectly. The best thing to do is get one from the AR-15. They're about $15, and the same size except 11 inches long. You'll want to cut it down, but man will that thing help.