IMR 4350 is generally a real good powder for anything on the 308 case - and the 260 is on the 308 case.
That being said I have tried many combinations of bullets with that powder in my DPMS LR 260 and the best it will due is 1.75". My other 260 (Encore) shoots very well (.6") with IMR 4831 and 140gr bullets. After giving up in frustration with the LR260, I was told that the LR prefers H4350, which I did not try (I tried 414, 4320, 380, IMR 4350, RL15 and AA2700). When the sky is blue the birds are chirping and everything is heavenly - I will break out the LR260 and try H4350. If it fails after that, the barrel comes off and it becomes a 6.5 Creedmoor.