I forgot on my first reply, where do you think there is plastic? The grip and cheek piece on the basic version is wood with a non slip covering called protouch, not to my taste, but very effective.
My wife uses an LG300 junior because she is small and the alutec was too long on the shortest setting and she prefers the feel of a wood stock. The LG300 is a superb rifle and I'm sure the LG400 will be better (if that is possible). The stocks on the 400 will be the same as the 300 but without the standard wood stock. The basic 400 is an alutec, the action is the same across the range, the other alutecs have better sights and more adjustable butt and cheek pieces which ups the price, the top one, the anatomic, has a different (all wood stock), no carbon one in the first catalogue. Unless you are shooting 590+ I doubt you would tell any difference between any of them 300 or 400.
Good shooting
Robin