No matter how you do it, its going to be a form of stock work. The two methods that come to mind are either 1) remove material from the stock in the barrel channel, or 2) epoxy bed the action and make spacers by wrapping electrical tape around the barrel in two places to keep it centered in the channel and also holding the barreled action higher, hence giving you more space between the barrel and stock.
Maybe someone else has a different effective method that I am unaware of and will hopefully chime in.
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