Depends... try as many as you can from friends and such.
My 6.5 Creedmoor has had standard, CMC 2&2, Armalite, RRA, KAC Match, SSA-E, SD-E, Triggertech, MBT-2S, AR Gold. It has the AR Gold in it and won't be changed. My 6mm Creedmoor has had a similar list, but I also tried an Elftmann...