When I think about bending but not breaking, I think of archery bows. To make a durable bow from many woods, including Osage Orange, one must never cut across a growth ring. In other words it has to have split right down the growth ring, or the outside of the bow (the face), will eventually fail catastrophically. Hickory is one wood that just doesn't care all that much about whether or not there has been some shaping that crosses growth rings. Some woods when hit with the axe will split right across growth rings because there is good adhesion between one years grow and the next. That makes the wood unsuitable.
So hickory was chosen for several reasons for ramrods. Available, strong, kind of workable (though stringy) and it resists splitting when bent. One poor quality is that it swells when wet more than many woods. So you're better off with a slightly crooked but undersized hickory rod than one that is tight in the thimbles.
If your split hardwood intended for ramrods is too crooked, straighten it some with heat just as you would a bow, or a snowshoe frame, or a fish net frame. The general rule is to steam green woods and use dry heat on seasoned woods.
