This cartridge was developed by Paul Middlestead of San Diego, California, and is based on the standard 243 Winchester case necked down to handle .224 inch bullet. The body dimensions remain unchanged, but the shoulder angle is increased to 30 degrees, thus resulting in a longer neck (0.300 inch vs. 0.241 inch). While staying on the upper end of the velocity spectrum, this cartridge gives up nothing in the accuracy department. Five shot 100 yard groups of 1/2 inch MOA are commonly reported. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.