Re: 308 winchester 155vlds or 168vlds
I would suggest you try both. If it were me, I would use the 155. These can be driven considerably faster than the 168 and despite the published BCs you will find them closer than you think (in the real world) + the velocity advantage. If you really want to go bigger than the 155 concider the 175 over the 168. This can be driven at near 168 speeds but hosts a MUCH better BC than either.
Hope that helps!
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.