The 7mm JRS is a wildcat from John R. Sundra, a writer for Guns & Ammo. It is a version of the .280 Remington Improved that gives near 7mm Rem Mag performance. The design uses the usual minimum body taper but gains maximum case capacity by pushing the shoulders forward. The 7mm JRS dispenses with the typical wildcat 40 degree shoulder for better case life and magazine feeding.
This text is based on information from “Cartridges of the
World”, Hodgdon reloading manual, the cartridge designer and/or