Sinclair Carbide Neck Expander Mandrels are ground from solid carbide stock, which yields closer tolerances and more lubricity. Carbide is also better at resisting galling which can leave behind material and scratch the inside of your necks.
The shape, finish, and size are the result of years of use and experimentation by many hand loaders. Sinclair expander mandrels are made .001″ smaller than bullet diameter. Using an expander mandrel prior to neck turning sizes the case to fit the neck turning mandrels perfectly, or use prior to bullet seating to get more concentric necks and perfect neck tension.
All Sinclair Mandrels are designed for use with the Sinclair Expander Die and all Sinclair Neck Turning Tools.