WMD Guns Bolt Assembly 6.5 Grendel Type ll NiB-X Nickel. WMD Guns designed these Bolt Carrier Groups to provide a superior locking and unlocking action with bolt extensions making this bolt assembly a vital part of your weapon build. The WMD Guns NIB-X Shot Peened Bolt Assembly is constructed out of shot peened case hardened 9310 steel and it's shot peened magnetic particle inspected to ensure the parts are free from imperfections. When you need a strong bolt assembly that will deliver premium performance look no further than the WMD Guns NIB-X Rifle Bolt Assembly. Specifications for WMD Guns NIB-X Bolt Assembly: Manufacturer: WMD Guns Finish: NiB-X Fabric/Material: 9310 Steel Package Contents: WMD Guns NIB-X Bolt Assembly WMD Guns 1-NIBXBA65: Bolt Assembly 6.5 Grendel Type ll NiB-X Nickel