Claro would be my guess.

black
claro usually has more figure
they are kissin cousins though

Sure looks like the claro on my Cooper.

Looks like black to me.

Here's another picture with a stock blank that looks almost identical in grain and color. Any guesses on the stock blank?

Black Walnut.

The origin of the gun will probably tell you the type of walnut. In the plainer grades it can be difficult to identify. If it's a Sako, it's European walnut. If its a Remchester, its American black walnut.
Is that you Irl?

Claro comes in plain vanilla too; this looks like Claro and so does your blank. If they came from California, then it probably is. Stock could be black walnut too; that varies tremendously depending on the conditions under which it grew.
There are only two kinds of Walnut; thick shell and thin shell; and within those you find the variations depending on where it grew. All of the "English" (thin shell called by many names) in the US is grafted onto Claro, usually, root stock.
Not sure why.
I see SDH said it; in the plainer grades it can be difficult to ID. Especially from a picture.

The rifle is a special order 1953 Model 70 Winchester. Winchester was still offering European walnut at that time as a special order option. The stock blank is a nice modest piece of Juglans Regia that's dated 1986. Yep it's me!

Here's another picture of the blank.

Not any thing I would consider using whatever it is, too much work involved to use that kind of wood on a custom rifle..it would be OK for a replacement stock wood but the cost of styling would void that, just buy a simi inlet. Off hand I would say its too porus to be European walnut, but ya never know.

Good, I won't feel bad about hacking it to splinters then. Grain size is pretty close to the same as the piece of NZ English walnut I have. Maybe the larger grain is a result of growing in a wetter climate?