I recently saw an extra barrel for a Mauser 66 for sale in caliber 9.3X64, which has a 12.60mm rim. My rifle is set up for the 8X68S, whose rim measures exactly 13mm.

I am wondering if the .40mm (.157") difference in the size of the rim of the two cartridges is small enough to allow a barrel in caliber 9.3X64 to be used in my action, Does anyone know how critical this dimension might be? The other interchangeable barrel I have for this rifle is in 7X66 SE vom Hofe, but its rim size is exactly the same as that of the 8X68S, so it offers no clue to the answer to my question.