You need a .473 bolthead. You can find then at many places. I bought a whole bolt from The Shooting Shack, they are in Texas. Thay sell boltheads among many other things. Are you going to do the change over yourself? If so, you will need a nut wrench, headspace gauges, barrelvise. I suggest you go over to SavageShooters.com, you can learn alot over there about the Savage/Stevens firearm. By the way where did you look for info? There may be a bunch of info on here, I'm still learning my way around here, hope this helps.