The original BR cartridge was chambered in a Remington 40x pistol for silhouette shooting. It was not until much latter someone got the bright idea to chamber this in a rifle. The problem was how do you keep someone from shooting a round meant for a rifle in a pistol, so what they did was make the neck longer so that it would not chamber in the pistol, and they called this new round the 6 mm BR Norma. The other cartridge keep the name of the 6mm Br Remington. So with that all said most dies will be marked 6mmBR Remington, but they will work fine for the longer necked Norma version.