I have the CA90TR Proline (not sportsline) and it double feeds a lot. I have had this issue and have never even touched the gearbox or hopup. What's strange is that it doublefeeds a lot on Full Auto (In bursts and holding the trigger down) with a box mag and a high cap. On Semi-Auto, I can shoot as fast as my finger hits the trigger and it will not double feed. I was just wondering if there is any fix to this issue. Any help would be much appreciated! Also, on another note, which iron sights would work best with a P90? I tried M4 sights (G&G/AGM) and I have been looking at the APS Flip Up sights on Evike (around 23 dollars each). Would those sights work in any way? I have a laylax rail in the front so it can house sights from multiple angles. Again any help would much be appreciated and I thank you in advance for helping me out!