Blackswamp,
While red oak is readily avalible, it is in my experience, prone to splitting.
One of my first field guns the cheeks split on the first or second shot.
I used those bolts with a wood screw on one end and machine screw on the other.
Those are hanger bolts for plants or something. Bad way to go.
If you run your bolts clean through, that will help.
I guess I did everything wrong at least once!
White oak may be avalible at a saw mill, or speciltilty lumber place.
That's a bit pricy, but a better material.
Of course drilling a straight (angular) hole without a drill press is problematic too.
I center drill where the hole is supposed to start, and end. Then I set a center under the spindle
with the far side of the hole located on it. Drill from both ends to meet in the middle.
You'll need an angle plate, and a couple of clamps to hold the cheek in place while drilling.
Works for me.
Good luck with your project.
Kap