This is 7mm Mauser (7x57) Hornady 139gr. SST (Super Shock Tip)Superformance Ammo. This is Hornady's brand new line of hunting ammunition. Superformance is a cutting edge technological advancement in ammunition design that transcends convention and achieves the highest performance of any ammunition on the market today. Superformance ammunition is 100 to 200 fps FASTER than any conventional ammunition on the market today, and achieves this performance in EVERY gun, WITHOUT increases in felt recoil, muzzle blast, temperature sensitivity, fouling or loss of accuracy. This ammo is brass cased and boxer primed. It comes packed in 20rd boxes.