As I have a M 1900 Mannlicher-Schoenauer that was rechambered in Britain from 6.5x54 to 6.5x55, reproofed in Birmingham 1984, I can only warn you from attempting it. The problem is not the bolt face, needing no alterations, but the magazine. The 6.5x55 has a fatter Body. So altering the opening, the spindle, the cartridge stop and the cartridge guide surfaces is necessary to make it feed halfway reliable. Mine still does't!