I have a 1:10 twist 300 WSM and initially was shooting 165 grain Interbonds and it grouped them very well. You should be fine shooting the 168's out of your 300 WM. I chose to go with the 185 grain Bergers for my WSM and it shoots so well I've had a hard time wanting to change anything else.
Chances are that they will shoot in a 13-1. The only way to know is to load some and try. I have heard some poeple swear by Burgers and some swear at them. I my self shoot bergers in my 270 Wby.
If you want to stretch that 300 try some 220 smk. If you are shooting beyond 650 or so they really do a good job.
Mickey
Nothing wrong with big bullets and Coues deer. I shoot 208gr in my 30 cal. I shoot 162gr in .284. I hope to have my 300 grainers ready for my Dec tag. I do know a lot of guys that run 165ish with a 1 in 10 twist .30 and they have no issues. It all fairness I've seen a lot of critters DRT with 168s in a 30 cal, mostly Coues and a few elk.
I have had excellent luck with the 168 berger vld in both 300 wm and mostly in 300 RUM. The rifles like 'em and they work very well on antelope/deer/elk out to 800 yds so far, see no need for heavier , and my rifles LOVE 'em. You can use heavier if you want, but shoot the one YOUR rifle likes and learn to shoot it.