L.E. Wilson 270 Caliber .276 Expanding Mandrel

An L.E. Wilson expanding mandrel for 270 caliber, .276 inch. Wilson's stated use case is new brass: running a mandrel through the neck of a factory fresh case before its first firing so every neck comes out at the same inside diameter.

New brass takes a beating in bulk shipping, and dented or out of round necks are common enough that mandrel work has become a normal first step for handloaders who care where neck tension lands. Consistent neck tension is what makes seating force consistent, and seating force is one of the few things at the bench you can feel go wrong. Check what you have to run the mandrel in before ordering.