You have both??the walnut stock is nice, for some reason it contains more heat then the fiberglass, most likely because the fiberglass is able to breathe easier. The walnut also swells and flexs more. Either way you will have a great rifle. My standard has a walnut stock, my squad has the fiberglass.
I've read that on multiple occasions about the accuracy getting worse after the barrel is hot.Couldnt hit crap after the barrel warmed up! Really, 6moa was a only a dream.