GG is one hundred percent exactly right about the rotars being caliber specific. Contact the Mannlicher Collectors Society (they are very service minded people, I happen to be a member)for advice. Some projects have not worked out and the magazine was pretty much trashed in trying particularly to enlarge to the bullet diameter of a larger cartridge. I was successful in going from 8x56 to 7x57, and also to 8x57. Don't tell my friends at MCS! Best to leave it ALONE and find another Mannlicher in the caliber which you desire. It would probably be just about impossible to find another magazine, by itself, which would facilitate the alteration. Great rifles, though! Steve