The N has nothing to do with the bore diameter . You need to slug your bore , as like all old military rifles , it will vary from rifle to rifle . You will need to know land and groove size . I have test fired my 22 8mm Lebel rifles and load about 1/2 with one bullet size and the other 1/2 with another . Your groove size should be about .326 to .330 , lands from .315 to .318 . An undersized .323 boattail will not stabilize well in a large bore and tend not to shoot well . I have used the .329 bullet in my large bore rifles for the best accuracy of any of mine . My RB groove was large at .329 . A easy on the rifle load is a .323 225 grain round nose , flat base at about 1800 to 2100 fps . If you use a light load of I-3031 powder , undersized Privi cases , and a small .323 dia bullet in a rifle with a large bore and chamber you will get a meltdown . The bullet will not seal up the chamber and bore and the powder will not burn correctly . The primer will jam the bullet in the bore and just melt the powder into a green lump . I-3031 is known for this in rifles with the above factors . Cold weather will also add to the factors , not really a problem right now in the summer .