Please observe the images here
http://www.picturetrail.com/sfx/album/view/17090409

The cracks at the apex of the lock inlet almost always start at the head of the stock related to a design flaw; inadequate wood surface area.

Comparisons with boxlock and other sidelock stock head surfaces may be seen here, including a Purdey courtesy of C.J. Opacek
http://www.picturetrail.com/sfx/album/view/15127852

This flaw can be rectified, or cracks prevented, by glasbedding
http://www.picturetrail.com/sfx/album/view/20576154

I am using a 1906 OE 16g Smith as my primary recreational skeet gun with RST 3/4 oz. loads. It has no cracks, and I have not prophylactically glasbedded the head of the stock. I did glasbed my 1908 12g pheasant gun however.

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