a good piece of wood will take up to 6 years to dry out below 4-6% humidity. Thats when it sits up in the rafters here in slower Arizona. Up north 7 plus %. When they get as low as can be expected thats when you seal them with boiled linseed oil. I saw on Y tube where some body wiped down thier walnut stock with walnut oil. I did not believe it but in the salad dressing section of my local safeway they have walnut oil for sale. Go figgure.
linseed oilworks best if its what was origonally used on the wood.
Beech/burch were an expedieant measure, not because they were of a lesser standard/quality than walnut but because walnut takes alot of effort and resources to process. long drying time. Lithgowwent thier own way with indigenous flora when thier walnut supply was exausted and none more was forthcomming from England
. Winchester ran into a similar problem with walnut on thier m1's. They got stuck using existing supplies to ramp up initial production. early winchester m1's were some of the most beautiful rifles ever.
The Germanplywood solution came about because thier advanced chemical industry in general and the wood glue side specifically was able to solve the problem and loosen up production bottlenecks.
In 2012 Roger Wedham wrote a book "The 2012 Complete book on Lee Enfield Accurizing" ISBN 978-1-4716-1465-1. in it he addresses issues relating to warped wood and using linseed oil to reverse the warping (page 53).