| Warning! Notes: Historical Notes: The 7mm JRS was designed by Jon R. Sundra. It is based on the 280/7mm Express Remington case, but is more than an Improved 280 in that it cannot be made by fire-forming 280 Remington ammo in a 7mm JRS chamber. Attempting to do so is dangerous because the 7mm JRS pushes a 35-degree shoulder more than 0.050-inch forward of where it would be on the 280 Improved. Therefore, headspace is increased commensurately. General Comments: Norma MRP and Reloader 22 are the best powders with H4831 and IMR 4831 and IMR 7828 coming in a close second. Other slow burners like IMR 4831 and H450 also do well. Depending on individual rifle and case (Remington, Norma or Winchester), maximum loads range between 60.5 to 63.5 grains of RL-22 with a 150-grain Nosler. Velocity has ranged from 3060 to 3120 fps in various barrels of 23.5 to 24 inches. (Cartridges of the World 11th Edition) |
