The .308 was developed around the 150 grain bullet weight but as time went on it became apparent that the optumum bullet weight was 168 gr. for best accuracy. I would also start by seating the bullet .050 off the lands as this is what TY at Barnes recommends. Then move it in or out by .005 to find tune the load. I happen to shoot the TTSX in the 168 gr weight and have found as many do, that Varget works very well with just about any bullet in that weight range and try to keep the velocity between 2500 & 2600 FPS. But by the same token if you were able to get the Scirocco & Nosler bullets to fly true with what your using for components, it maybe as simple as moving the seating of the Barnes a little to tune it in. I would give that a go before anything.