IIRC what you're wanting to do isn't possible as I believe the bore diameter for the bolt and the depth of the raceways in the action are different than what would be needed for a centerfire rifle bolt assembly. I also don't think finding workable bottom metal for a DBM would be possible as the 220 has the long-actions crew spacing but the bottom of the action is cut for short-action length magazines making it kind of a bastard. It's been 12 years since I last played with a 220, but I'm betting Fred would know for sure.