The Winchester USA Rifle Ammo 5.56mm 55 gr. FMJ 20 rd. from the long-standing USA White Box series brings straightforward, reliable performance for range days and training sessions, and if youre looking for a go-to 5.56x45mm NATO load this cartridge delivers consistent 3180 fps velocity and about 1235 ft lbs of muzzle energy from a 55 gr full metal jacket lead core bullet, which shooters trust for target shooting, load development, and practice across AR-platform rifles and bolt guns chambered for 5.56. With brass casings and a design that feeds and cycles smoothly, this Winchester ammunition reduces stoppages and gives you repeatable trajectories for zeroing and follow-up shots, while being made in the United States to meet common shooter expectations for quality and sourcing. If you coach at the range, run training drills, or spend weekends working on marksmanship, the USA White Box lineup is economical without sacrificing ballistic consistency, and its FMJ profile keeps impacts predictable on paper and steel targets. For those shopping Winchester 5.56 ammo, this 55 gr FMJ option is a practical choice for reliable range performance and consistent velocities.