Hornady Lock-N-Load modified cases for use with the O.A.L. these specially prepared modified cases are threaded at the case-head and have a .002" oversized neck to accept the same bullets you intend to load. This is critical, as the Lock-N-Load® O.A.L. Gauge dimensions obtained will be accurate to .001". These results cannot be attained with competitive products, which use a simulated bullet with an arbitrary shape.