RCBS Small Base Sizer Die Set for 308 WinchesterRCBS Small Base Sizer Die Set 308 Win. The RCBS Small Base Sizer Die Set for 308 Winchester cartridges is designed to ensure optimal chambering and reliable function in semi automatic, pump action, and lever action rifles. Precision engineered, this die set provides small base sizing that reduces the case diameter slightly below standard dimensions, offering consistent shoulder setback for dependable reloads. The included expander decapping unit