I had the same crack on a rifle I bought once. I took a piece of .020'' lightly perforated steel shim stock 4'' long that fit the 3 bottom flats of the barrel real close. I embed this into the barrel groove over the crack so it set just a smidgen below into the stock under the barrel. I prepared my 30 minute epoxy with fine walnut dust , as this gives a little darker color , but gives binding fibers to the blend. I darken and solidify to taste with drops old english polish. Once the goo is ready I fixture stock down, paste the cracks if seperated , if stock still holding together, force glue into cracks. Then trowel some to the bottom of the undercut in the stock for the shim, place shim in puddle , then more goo over it . I then lay a piece of cling wrap over to protect the barrel from binding to glue goo. Assemble barrel to stock. Pin in place . Wipe off excess that will be flowing out from the channel area that you glued. Easy wipe off with low test alcohol from the medicine cabinet with multiple soft cloths . I use alcohol dipped ear swabs to clean area where it will overflow from the under barrel wrap. Moneture the project over the next hour for excess that still will squeeze out, let sit 24 hours, then gingerly remove barrel . Note that perforated shim stock piece should be douched down well with alcohol then let dry before insertion with minimal finger prints on it to ensure nest binding . If this is made properly with all three flats , perforations are patterned, it will be very strong and can not be bent by hand easily as like channel iron. I had five breaks on mine, it was heartbreaking. But now she is looking good, can hardly tell of her misfortune.
