What follows is based only on my experience. With a 308 you normally get a "low node" and a "high node" of accuracy during load workup, the "low node" is usually between 2550 and 2650 fps and the "high node" is between 2700 and 2800 fps. There seems to be a transition point between the two nodes that is a "scatter node" where the bullet timing and barrel harmonics just don't work out right.
I assume that since you spent the money on a 26" barrel for your rig you would want the velocity advantage of the "high node" for long range shooting. Once you get past 600 yards, velocity matters more. I don't know if you plan on shooting that far, but normally a 178gr BTHP over a heavy charge of Re15 is a 1K load. If you were shooting 600 and under the 168 BTHPs are a lot cheaper.
Try loading up 5 shots of #4 to test the low node, and 5 shots of #8 or 9 to test the high node. Wait 5 minutes between shots if you can to keep your barrel cool.