I wish I had taken pictures of a Smith stock that was given to me to dispose of. I took it to a band saw and cut it in one inch or less segments noting how thin the wood got in each segment. In a couple of places it was just a fat Popsicle stick in thickness. Mass produced guns are in-let more than needed in some places. If hand inlet the amount removed would be less but the cost go way up. The Smith in-letter had to do five, ten or more a day not one a day like a custom stocker. Hence extra wood needed to be removed because time did not permit otherwise. And they lasted under normal use for years before cracks became an issue otherwise they would have been forced to make changes to keep selling new guns.

Smiths crack because the wood left after in-letting is too thin to transmit the recoil from the action to the shoulder. It compresses, it flexes, it cracks. Not all the time, but a very high percentage of stocks will fail. Add loads with excessive recoil, over oiling and failure to do routine maintenance to keep everything tight as possible and cracks are inevitable.

Other guns have similar problems. Remington 1894 and 1900's split at the head at a very high rate. The repair is fairly easy and last, but a better inlet design and change of how the wood fit into the back of the receiver could have eliminated this issue. I suspect half of those I have seen have split stocks and every one I have pulled the stocks on have them (cracks), wither seen from the outside or not. The cracks are there even if you do not see the stock spreading.

To me a Smith crack is almost a bargaining point to a buyer. Drop the price because I see a crack in the stock. You know they are there and look for them. They are not so bad the gun can not be shot so are as much a cosmetic problem as a functional one.