Changing Calibers The Blaser R8 is a modular system capable of switching barrels. When changing from one caliber to another within the same caliber family, no bolt head change is necessary. If going outside of the caliber group during a barrel exchange, the bolt head has to be changed as well. However, the bolt head can be exchanged quickly and easily. NOTE: Except for the Blaser Saddle Mount, no R8 components are interchangeable with R93 components. Blaser R8 Barrel 6.5 Creedmoor Threaded M15X1 80103998