.300 Winchester Magnum Fluted Match Grade Barrel for Blaser R8 rifles. Changing Calibers Like the Blaser R93, 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 .300 Win Mag M18x1 Thread Fluted Match Barrel w/Magazine 80103504