A lot of competitors shooting the M1A1 use synthetic stocks, but I agree the M14 wasn't the best choice for economic and logistical reasons, and the trend towards smaller caliber infantry weapons had it doomed early on. Nevertheless an M1A1 is on my bucket list.Good article and enjoyed reading it. And as much as I love walnut furniture it simply wasn't going to make it for military use once plastics were available. For starters, it costs a whole lot more. It takes about 30years for a walnut tree to reach a size that is suitable for harvesting gun stocks in high volume. You can only plant about 100 trees/acre, and which will require periodic thinning. Then you've got the costs of logging, drying (takes about a year +), selecting suitable blanks (expert eyeballs), machining (figure 25% waste), and so on. All of it very labor intensive. The military, as we know, has to fight for every budget dollar, so wood is going to loose to plastic every time.
Here's a little about growing walnut for profit:
Growing Walnut Trees For Profit - Profitable Plants Digest