Easy-to-install crank knob, guarantees grip in any situation. Buy a decent Nordicshot knob here and the bolt will start moving. You can choose from three different sizes, all of which have three different models.
These knobs fit, for example, the following models:
Blaser R8, Blaser R93, Browning Maral, Merkel RX Helix Speedster, as well as other rifle models with an M6 thread.