Depends on the bullet. Hornady suggests 1:12 as the optimum twist for their new 178 gr ELD-X bullets. I've fired them in 12 and 10 twist 308 and 30-06 barrels with equal accuracy. They recommend 1:10 twist for any of their 30 caliber bullets 200 gr and above.
I doubt if you'll notice any real difference between 11 and 10 twists. I'd think you should be able to shoot 180 NPT's in the Tikka. Something ain't right. My load manuals say 2.86 is suggested OAL for 300 WSM and I often load them a bit longer for my Winchester. I have 180 Accubonds and 200 gr ELD-X's at 2.90".
I normally don't pay much attention to OAL. I load them to just fit the magazine then I chamber a round. If it bumps the lands I seat deeper until it doesn't. Wherever that is, is OAL. If they shoot well, and they usually do I leave well enough alone. If not I may experiment seating deeper, but that almost never helps.