I am not sure where this post belongs so here goes.This question is addressed to 8400 Kimber Rifle owners.
1)Has anyone measured their OAL and found it 2.872.5 or there abouts?
2)What length are you setting your loads say for a 165 Hornaday IB and 165 Nosler Part.?
3)Did lengthening out the shell help your Group or no?
4)What grain bullet does your rifle shot best in 300WSM?

The Kimber 8400 is ideal for having the option of a long magazine so that we can seat the bullets to the lands if we want to.

Each rifle is an individual so try various seating depths. The Nosler manual gives a suggestion on how to find this depth. Vary it from there to see what shoots best.

Smoke'em to see, and back off .30
Every chamber is different.