Fix the reason it cracked along with cosmetically fixing up the crack.
Most likely the bedding of the recoil lug on the bottom of the recv'r is not in contact with stock.
When the rifle recoils upon firing, the action just slams backwards in the stock. The rear upper tang of the action acts like a wedge against the wood and splits it like a piece of firewood.
That tang looks like it has clearance in the pic but I can't see the extreme rear of it, nor how it sits down in the inlet. Another factor is the rear tang screw itself. That can split the wood if the action shifts in the stock. The screw should be a slip fit thru the metal ferrel in the wood and not jammed into it. But even if a sliding fit when you put the rifle together, again if the assembly shifts when fired,,that screw and ferrel will act as a wedge toward the rear and split the stock thru the wrist even if there is clearance behind the tang itself
Should be bedded tightly at the recoil lug so the recv'r can't set back on firing. The action screws tight, the rear tang should have some clearance betw it and the wood around the back end (no contact).
The bottom of the rear tang can be bedded to avoid the action being pulled down into the stock any further than you want it to when the rear screw is tightened.
Old stocks need some help generally getting their original inlet specs back after years of pounding from recoil, over tightening screws, oil soaking and softening of the wood, ect.
Don't use the back of the magazine box as an extra recoil lug, that'll generally just crack the thin web of wood betw the mag cut out and the trigger cut out. That area may be cracked already.
You can cut under neath the cracked portion and hollow it out from the tang cut to better be able to get your favorite stock epoxy glue in there, & even a reinforcement pin.
Done carefully, nothing will show on the outside and it will be easier to pull the crack closed with the wood removed. The glue (epoxy) will be much stronger than the original wood in there.
Any oil or oil soaked wood has to be attended to. Glue and oil don't do well together and all the work is a waste of time if you don't remove oil from the wood first.
If it's just a little wisp of oil on the surfaces,,an acetone soak or wipedown(s) will generally do. Heavily oil soaked thru, I use the excellent but slow process of whiting powder coatings to draw it out.
The latter is not an overnite thing, but it works.
The stock can deffinetly be saved.
