I think Chris is on the money about the stress. It may just be the lighting, but it looks like there is a little more barrel flat showing at the far right and far left edges of the picture. Could it be that the barrel channel inletting in the vicinity of the crack was a little too deep and when the stock and barrel were pushed together, it over-stressed the stock at that point, cracking it? If this is the case, you could get things lined back up, which would close the crack some, then glass-bed the barrel channel and glue in a patch as needed.
-Ron