The OKH uses a .30-06 size pattern case where as the Jefferey uses the .530" base size unbelted case of the .404 but with quite a bit more body taper.I don't remember an O.A.L. for the .333 Jefferey, but with the 300's it will need a 3.500" magazine box length. I have had one original rifle and associated with 2 others and they where all magnum size Mausers.