Assuming you dont have them already, a clamping feedneck and a better barrel are a must. Also, you should make sure you have a hopper that can keep up with your rate of fire. from their, i'd probably switch from CO2 to HPA/N2 (assuming you still use CO2). Most regulators will require HPA/N2. You can spend a lot of money upgrading one but id start out with a feedneck, barrel, and a good hopper first.