Sothere:
Just ocurred to me that "incipient" failure of wood may be gun specific to a degree; i.e., some makes may be notorious for one deficiency in integrity or another. For example, Smiths have lockplates which are not champfered at the edges (square-edged and set in square-shouldered mortise)and cracking behind the plates is commonly seen. Lefevers (not a sidelock but inletted to a degree as if it were) show up with bits of wood sheered off adjacent to the top tang and fences. Fairly common in boxlocks also; perhaps stocks which are not tight or have differential bearing of the stock head or horns on the action back or fences and/or are shot with heavy loads are prone to breaks there. No matter how strait-grained the wood and despite any possible orientation of long-grain in the head, the run of grain at the top of the head is interrupted by the dip or valley which is the shape of the head and grip back to the thumbhole or beginning of the comb. Toes of stock are vulnerable for the same reason (easier to split a bolt of firewood 18" long than it is to split a tree end to end). The inclusion of knots in stock or forend is a potential source of drying cracks. The failure I dislike and distrust the most is an incipient crack running perpendicular to the grain one or both sides of the inletting at the wrist--what would be called in some quarters a "weather check" (sometimes caused by wind or felling damage while the stick is still in the timber but likely also caused by the inability of a very thin-walled stock exterior to flex without fracture upon firing the gun). This one won't remain "incipient".
Careful selection of stock blanks, ingenious design and painstaking execution limit the mechanical stress on a non-homogenous material but don't eliminate it. Nature of the beast.
jack
