How I repair a cracked model12, 1897, or similar stock

I have another model 12 stock to fix. This one is personal, and came from my father-in-law's grandparents. Grandpa bought a 12 gauge for him and a 16 gauge for grandma. The 12 gauge serial is 1930, and the 16 gauge is 1918. Both are in need for some TLC. The 12 gauge has a cracked wrist in the usual manner for this design, some crusty old grease-soaked surface rust, but no pitting, and <10% of its original finish left anywhere. I think the 16 gauge was refinished once before, but I'm only about 80% certain. I plan to get both running again for my son and daughter, and making sure they will run for at least another 3 generations.

I've done many of these stock repairs now, so I thought I should share my experience of how I go about it. Here is our starting point.
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Before we fix it, let's talk about how it happens, and what to do to prevent it should you have a rare un-cracked stock. Compressed wood fibers in the end grain soak up oil over the years, causing the stock to feel loose. Next time it gets reassembled and tightened, the tang acts like a wedge under recoil and a crack forms. If there appears to be two cracks on the same side, it's likely a splinter popping up because the shoulder of the stock is in contact with the receiver - same cause though, the stock was tightened up due to oil-softened fibers until the shoulder made contact and gave under recoil.
The simplest way to prevent this is to store your shotgun with the stock bolt loosened a bit. Same goes for any wood-bedded stock. Action screws loose on bolt guns, trigger guards open on Garands, stock bolts loosened on enfields, etc. Tighten em up before you prep for the range, loosen them as part of your cleaning routine after.
If the damage is already done but no crack has formed yet, you can glass bed the butt or skim-coat the end grain to seal it.

Ok - here is how to repair the damage. First, I mark the face and sides with a grease pencil. Our goal is to drill through the sides of the neck and epoxy-in-place threaded rods - in this case number 6 stainless machine screws.
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Many would drill straight through the neck, but this would be visible, so our goal is to drill from the face at an angle to hide the repair a much as possible. I use a pointed carbide burr followed by a rounded cone burr on a dremmel to dimple where the start of my holes will be. We don't want any wandering when we drill our holes as there is very little room for error.
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Tape off the depth of each hole, and make a pilot with a smaller drill, and work your way up to the target diameter. Always use a hand drill. You can feel it chasing the hole and don't need to worry about it wandering. My final hole was to be 11/64, so I started with 3/32, then 1/8, and final chase with the 11/64. Don't rush if you want clean holes.
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Screws fit with a loose jiggle. Cut them to length below flush and set aside.
Now comes the part that is painful to watch. We split the stock open the rest of the way. You can probably avoid this if you drilled all the way through the neck, but you need somewhere for air to escape when you push in your rod and epoxy, otherwise the repair likely won't hold. But then you will have dots of epoxy on top and bottom, and the crack will still be visible, and the repair is not as strong.
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Now we are ready. For this type of repair, I like the original acraglas instead of the gel. The original is thin and runs everywhere, easily to the bottom of the crack. The bigger the mess, the more effective the repair! Dye the acraglas black with a drop of the dye. On a light colored stock, you maybe want the brown dye, but I've always worded with walnut, and trust me you want to dye the repair black to make the repair disappear in the grain pattern after you apply finish in the end. Make sure to work the epoxy into the crack. Pour and push more epoxy into the holes while the crack is spread open. Then remove the wedge, gently press together but not all the way. Dip the threaded rods into epoxy and fully coat them before pushing them down in the holes. Add more epoxy to the face of the stock until you can't see the holes. Now Put the clamp on. Clean off any major excess that is dripping down, but don't touch what has oozed out along the crack. You can also scrape away any excess you can reach inside the hole. Yes I taped off areas around the crack (but not the crack itself) to make cleanup easier.

Now we bed the receiver to the butt. With the stock vertical, plenty of release agent on the receiver, and plumber's putty filling in the trigger-guard screw and the other hole in the rear of the receiver, slide it into the stock.
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Add a shim made from a folded over notecard (double thick notecard) to set a small gap between the shoulder and the receiver. Once it is set, I'll remove the receiver and use a very sharp chisel to remove the notecard shims and epoxy from the outer shoulder areas, making the ring and inside bear the full recoil, as designed.

If there was also a shoulder splinter, I would have pried it open to work epoxy in and use rubber surgical tubing instead of a clamp to hold it all tight.