That crack looks like it would be easy to get to from the back of the bottom metal inlet.

I'd see how far the crack went. I'd drill holes thru the crack from inside the inlet, hopefully to fully encompass the crack. I'd then work Acraglas Gel (brown dye) into the crack, making sure I got the gap fully filled.

Then, I'd patch the finish with Tru Oil. To fully eliminate the crack, you'd have to refinish the stock.

I'd glass bed the action to stop any future movement. I'd be sure all stress was relieved, leaving a slight gap behind the bottom metal and behind the tang.

DF