Another factor to consider: if the .300 WM is going to be used for prone shooting, make sure to consider bipod weight. I am a big fan of Harris bipods. They are very durable. When hunting in western USA I use a bipod for shots over 150 yards. A Harris bipod will weigh 14-20 Oz. So an ultralight rifle, with a good scope for longer range shooting and a bipod is still going to get into the 9 lbs range. My Kimber is 8 lbs 8 Oz with scope and no bipod. Add a Harris and I am at mid 9 lbs.
My blaser R8 is 7 lbs 5 Oz without the scope or bipod. The scope (20 Oz) scope mount (6 Oz) and blaser Carbon bipod (5 Oz)will bring it to the same weight.
If you go with a carbon bipod and one of the rifles you are looking at, you should be in the mid to low 8’s. Not a lot of difference.
so, if weight is the primary goal, make sure to go all in with light scope mounts, a simple and very light scope, and a carbon bipod.
I bet you know all of this considering the quality of rifles you are looking at.
Due to a scope failure on my Kimber this last fall year I used my son’s Kimber hunter in 6.5 CM. It weights 7 lbs with scope and no bipod, or 8 lbs 4 Oz with bipod. The weight difference was only slightly noticeable.