In some cases the barrel and it's interaction with the stock is an integral part of it's accuracy. This is seen with practices of bedding and shimming, but stocks were also designed with the rifle. I know that No4s in particular were redesigned under some of the most scrutinizing scientific technology of the time, in particular with slow motion photography and even by analyzing series of still photos of the rifle during firing. It was found that the bullet in some respects rides a wave down the barrel. The stock was designed to at once help the barrel contain and direct this wave. This was also true for the SVT-40 series of rifles. They seem "lanky" and "fragile" to us, but the design was intentional and functional.