Superglue will work wonders when wicked into cracks until they won't hold any more. I use it on cracks on wood bows, even with a limb flexing I have never had a crack open back up.
On a lock mortise that split out really badly when a drill bit wandered and the pin tried to go out a toothpick plugged hole I super glued the crack, gave it a tight string wrap and proceeded to finish the rifle after the glue dried.
The crack was 1" long with large splinters of wood knocked out, I fit the pieces back together like a jigsaw puzzle. The first picture shows the repaired crack and bad exit hole plugged.
The last picture is the finished guns lock molding and now almost invisible crack.
View attachment 32768
View attachment 32767View attachment 32769