Re: 175smk vs 168 barnes
Its hard to change something that seems to work so good, but the 175 SMK at the same velocity will perform a little better at extended ranges. Better meening a little flatter and a little less drift, but not a huge amount. Killing performance on big game would depend on the range.
The 175 SMK at the same velocity as the 168 will get you much farther than the 168. Mayee a couple to a few hundred yards before going unstable.
Hope that helps some
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, 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.