Am cataloging some new made pistol cartridges and notice a big difference in the color of Brass primers. Was wondering if anyone knows what brass formulas different manufactures now use for primer cups. Many rimfire cartridge cases over the years use the standard “cartridge brass” ie: 70-30 copper-zinc mixture. Others have used 68-32 and 65-35 mixture to make what is commonly called Red Brass. Several of the primers on the catrridges cataloged are more red than others. Am not confusing primer seal with the primer material. Don’t need any smart mouth to comment that my main collection is 31.