Walnut is an amazing ood and the capabilities of a piece can be almost anything.. Only a few generallities exist.
English or thin shell has fewer pores or at least smaller pores. These were the transport tubes when the wood in question was growing and form the base structure of the wood much as beams in an building do. This lack of porosity gives a much finer texture and is hat gives the wood it's wonderful finishing and checkering qualities. Properly prepared it is hard and very dense. In some forms (area where the tree grew) it is darker and makes the best stock (as a rule) for heavy recoiling rifles. I have a piece in the shop right now that's gorgeous and very fine testured. Unfortunately it was kiln dried from a very wet(likely as cut) state. The cells which make up the majority of the woods bulk were exploded. The stick is a beautiful marble cake figure, ranging from a light brown up thru dark dark chocolat swirls.. It is extremely light. It will still make a fine stock but will likely not stand up well to heavy recoil..
Claro i a black walnut variety that grows extremely fast. It is fairly pretty (lots of figure) and is fairl strong. It is a little brittle and this can make it a poor choice for a hard kicker but the abundance of figured wood brings down the price some and for a 250-3000 it would be my choice. It checkers well but not as well as English.
Black walnut is a fine stock wood. It's extremely variable and acn range from fairly light to nearly inpossible to work! I've some in the hop that's over 75 years old.. It's never been in a kiln and is so hard it's a pain to workwith but is tough as nails...literally. By far the most common figure is crotch (where the tree knits together a fork in the trunk). With the rest being much rarer. The rearest is burl. True burl is a swirling pattern caused by growth bud(s) growning inside the slab. It is not often found today and would likely rate a 'special selection' rating. This wood has been acclained the best of stock woods but has faults. It's porosity makes it a bit more suseptible to oil rot where its in contact with metal. It alos makes this wood a bit less stable than english..or perhaps even claro. It checkers fairly well and is quite rsistant to splitting.
Bastogne is a steril cross between black walnut and English.. I makes some fantastic figure. It is fairly uncommon, but a good stock wood. Much more figural than black and just a bit more pores than english.. I have noticed a tendancy for this stuff to have more oft spots?? Don't know the cause but to a checkerer it is a pain. It results in the checkering creating fuzz as the tool makes the grooves. These can be from very minor to being such a problem they completely hide the work. They are generally removed by singeing with an open flame..
The other woods make good stocks but most such as sycamore are fairly plain.. Hard maple is an exception. Mostly fiddle back but shell flame and birdseyes are not uncommon.. The ood is horribly difficult to work and the stocks a bit heavier than walnut but it can be stained and makes a very beautiful stock..
-All of the above have their exceptions. Wood is a growing thing and as such can and does profuce variations.. Firure in a stock should always(with one exception) be conined to the butt stock as it is not as strong as straight grain. So a really pretty piece of wood can be ruined(at least damaged) by poor layout.. The exception is fiddle back. It actually strngthens the ood a bit and can be full length of a stock. It's more common and is my personnal favaorite. For a 250-3000 I would use a nice piece of claro. It's a bit cheaper than good english and a bit lighter. While more brittle it will undoubtedly be sufficient for a 250 savage.. where its lighter weight can make the rifle even handier... As to checkering I always remind folks that to do it job it likely should stay about the 20-24 LPI range. Finer and it's usefullness is diminished, courser tends to look a little crude.. Remember books have been written about this subject(inckluding this one) but the main thing is to find a blankwith decent grain flow and get a well designed stock.,.and enjoy..