88mauser: I doubt you will be able to go from 6.5 to 375 if you have the rotary Schoenauer magazine. It Would require way to much reshaping of the caliber specific rotary spindle where in holds the bullet. MS rifles are notorious for feeding problems when cartridges are changed from the original. You would be very fortunate to find a rotary magazine available in 375 caliber. Better check that before changing the caliber of the barrel!! I am not sure what magazine your rifle has, however, and am refering to the commercial Mannlicher Schoenauer. Just a helpful caution...Steve