The proper way to remove the bedding is to use a milling machine and accurately mill it out with the stock solidly held in a proper vise. A handheld Dremel is not your friend for accurate work especially around the stockline. Others have suggested that part of the beding be left in to provide a foundation for the new bedding job, I would also agree with this approach as long as the new bedding is compatible with the existing one. Also head the warning about using a mask. If you use a Dremel use burrs that are designed for aluminium, wood and plastic work or they will heat the existing bedding and plug up your burrs.
bigbull