Product Information:

To use the Lock-n-Load O.A.L gauge, you will need a modified case (sold separately) to fit your firarm's chamber and thread it onto the gauge. 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.