An excellent load that I have found for the Encore .308 in a 26" Heavy Barrel, is 45 Grains of RL15, 150 Grain Sierra Pro Hunter, sparked by a CCI200 Primer. This load shoots consistent 3/4 groups are better off the bench at 100. Average Velocity has been 2841 FPS.
Double checking the scope last Sunday for an upcoming trip, this load off the bench produced a .860 3 shoot group at 200 yards. I'm not sure you can do much better than that...
Another Sub-MOA load for this barrels is 45 grains of Varget, Remington 150 Bulk Core Lokt's and again sparked by CCI 200 primers.
Both of these loads are 2/10 of a grain over max in the Sierra #5 book, however they are a 1 grain or more under max in other manuals.
Start low, and work up to it and see how it reacts in your firearm.
~ Bill ~