Check with the spring chart, the 140 at 380fps is just about right. If your looking for 320-330 try a PDI 120, and try to stay with PDI, I put a Prometheos MS 120 in my gun, the place that I bought to from said that it would do about the 360-370 area, it shoots at almost 440fps.
http://www.airsoftcanada.com/SpringChart.html