The barrel is held in the reciever by one screw that is under the action. After you remove the barreled action from the stock, you loosen that one screw and the barrel slides out. Slide the new one in and tighten the screw and you're done. You can modify the original stock if you wish, instead of buying a new one. Just use a 1" dowel rod or piece of pipe with some coarse sandpaper wrapped around itand enlarge the barrel channel in the wood stock.
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