What bullets have you shot through it? I have two 26 noslers. first barrel had horrible issues with accuracy with the first one. 135 bergers 12" at 100 yards. 147 elds were ok, but not good. Nosler factory ammo was consistent 2MOA or larger. ER shaw barrel. I called ER shaw and complained etc, but didnt really want to pay to ship back a $250 barrel. So i kept messing with it. 120 nosler Etip handloads were pretty good. 127 LRX over retumbo and all of a sudden had great rifle. 0.5-.75 MOA 3450 fps very low SDs. dead moose at 700 yds, dead mulie at 700 yds, dead rocks out to 950 or 1000. Same barrel, did nothing to it.
Bought another savage and rebarreled it with an X-caliber in stainless 26 nosler. Am 30 or so rounds in already shooting sub MOA. What did i do different? Went straight to retumbo and 127 LRX. I would not waste time with cup and core bullets. I know some people have got them to shoot well, but I have not. Load is mid 70s gr of retumbo, 215 federal primers and 127 LRX. If that doesnt show some promise after adjusting seating depth, send back barrel. But, i would be suprised if it doesnt do better than the factory ammo.