If no one else jumps in with info, you could check Nosler's site for 280AI load data, but they don't show the 168, just the 160 and 175. You would have to interpolate.
You might try RL17. It could be real good in that case. I would start @ 50 gr with RL17 which should give you about 80% capacity. Or, you could fill a case to the shoulder, dump it and weigh it and go with 80% of that.
-Mark