Sierra .22 55GR Spitzer Boat Tail Super Roo (1000PK)GameKing. In rifles chambering 22 calibre cartridges of moderate to large powder capacity, this famous bullet is perhaps the most efficient 22 calibre bullet available for varmints at long range or targets. The spitzer boat tail design provides exceptional accuracy and a flat trajectory. The high ballistic coefficient of this bullet provides less sensitivity to crosswinds and vertical winds and greater retained velocity and energy downrange. It is an