In my SX2 with a 28" barrel, something in the .670 to .680 range always does best. I have several chokes ranging from Kick's, Stardot, IC, CNC, Jellyhead, Rhino, and Trulock. I shoot a Trulock in mine right now. I have both a .670 and a .680 in the Trulock and both shoot well (and consistent), which is what I will use this year if I pack the SX2. With the 3.5" LB #4s I average around 135/10", and with the LB 3.5" #5s I average around 175/10". I also have a Kick's .675 that does well with most lead loads.