The 243 case will work for the 6.5 Arisaka. The body of the 243 case is slightly larger [.025"] at the base, just above the extractor groove than is the Jap case, so on the trip through the resizing die, a fair amount of muscle will be needed to swage the case head down a bit. [the difference is: 243 -.473"; Arisaka - .448"] You also will need to trim for length. As has been mentioned, it is easier to buy the Norma cases. Regards, Eagleye.