[Slater]

The following is from MIL-W-13871B "Military Specification, Wood Blanks For Small Arms" (which is curiously still listed as an active document in this world of synthetic stocks):

3.1 Species

3.1.1 Type I. Walnut shall be either black walnut (Juglans nigra) or English walnut (Juglans regia). When English walnut is furnished, it shall have a minimum specific gravity of 0.51 at 6 to 8 per cent moisture content, when tested as specified in 4.6.2.1.

3.1.2 Type II. Birch shall be either yellow birch (Betula alleghaniensis) or sweet birch (Betula lenta).


Are the walnut types similar as far as cost?

[Jeff F]

I don't know about the English walnut, but the last hunk of black walnut I purchased for a project was big $$.

[Sunray]

"...similar as far as cost..." Not really. It's got to do with the number of trees left that are big enough to harvest. American black walnut trees are getting scarce as they grow slowly. English walnut is more expensive than American though. All of them depend on the quality of the blank. More figuring or a strighter grain costs more.
Birch was used on M-1's, etc for this reason too. Not enough walnut for millions of rifles.
A net search for stock blanks will give you an idea of prices. One guy says English walnut blanks run from $50 to $1500. Turkish Circassian Walnut Stock Blanks start at $300, but that's for rather fancy wood. And it's for a slab of wood that hasn't been touched other than cut to a basic dimension. Have a look at these for an idea. Friggin' things are pretty just as they are. http://www.gunstocks.com/Blanks02.html