FREE BORE
A portion of the chamber, usually cylindrical, forward of the case mouth of a diameter larger than the projectile in which rifling is not present.
There are a lot of cartridges that have a cone shaped entry into the barrel vs having a parallel freebore. I have asked about this a few times on different websites. I’ve never gotten any useful information about it.
You didn't say what 338 but if you are talking a big 338, you need to forget about one rifle for both cartridges.
But of the two actions listed, the Deviant is the best choice.
I am an old guy. I grew up on a small farm that raised chickens. We produced about 40,000 chickens every couple of months. I eat chicken almost every day. I had some a couple hours ago, It was tasty,
Have you measured the diameter of the brass at the .200" line? Lapua brass normally has a larger diameter than other brass. Some Gunsmiths use a different reamer for cartridges using Lapua brass.