Blocks of wood, or"blanks," for gun stocks range from $90 to $2,800 or more for one, in addition to the custom-fitting charge of $1,500 for a rifle or $1,800 for a shotgun.

The 98 cents’ worth of plastic shims that came with your new $1,800 semiauto might be the most important part of the whole shotgun. Stock shims let you fine-tune cast and drop to get a perfect ...