Thread: Opening out the barrel channel on a carbon stock

Was at Southfort the other day and asked about the exact same thing. Broom handle (or similar) and sand paper was the answer. The "filler" (core or the stock) is an epoxy that bonds to the carbon shell and is non porous (so will not absorb water). They actually machine out the barrel channel after the stock has been formed.
I can't comment on other makes of stock. As stated, best to contact the manufacturer.