Here are a few shots of the wrist area, there's a little glare on the second one but it's 1.100 and you can a small crack that has already developed. I guess my biggest concern is as was set up in .36 caliber with 47 inches with one-inch flats and I'm guessing the barrel weights over 10 lbs so there would be minimal recoil. If I were to go with a .45 and a 32-34 inch barrel the recoil would be heaver. Granted I could put a new 32 or 36 barrel on it but I already have a .32 rifle now. Here in my state a .40 is the smallest you can use on deer but I personally think a .40 is too small.I spent a good portion of my life up in Maine and guns with back action locks were very common, specially smoothbores. I have a number including 3 made in Augusta and can see no issues with a back action lock significantly weakening a stock with average usage. Now if you were going to beat a black bear or moose to death I might expect it to break but I'm getting too old to hunt that way. You mentioned the stock being delicate and that may be the limiting factor but again I wouldn't worry about the lock inlet so much. Have you considered having it lined to a smaller caliber?