I agree with all, but I also think the 175 is probably more bullet than you might need for 500yd. .308 FGMM (Federal Gold Medal Match) 168 is going to be a hard load to beat with handloading. The 175 is 308 FGMM2; it gains advantage beyond 800yd.
True, the 168 SMK will work well out to 500, even in a 12" twist. On the other hand, a 10" twisted 175 gives up nothing, not to mention the increased B.C.
And we all know how this long range thing works, get good out to 500, hmm, let's try 600..then 700...
The OP may be limited to 500 at the moment, that could change. A lot of FT-R is shot at 600, where the 168 starts to lose it's luster. Regardless, a 10" twist is a very good twist rate for a .308.