This ammunition is essentially the same as the M193 ammo the U.S. Armed Forces would issue for the M4 carbine. That means it has a non-expanding and nonmagnetic full metal jacket projectile, with a cannelure that keeps it securely purchased against the case mouth until ignition. The 55 grain FMJ is the most popular bullet for AR-15s owing to its economical design and great accuracy!
This is not reloaded ammunition. Its brass cases are brand new – they’re just a little gray around their mouths because they were heat-treated at the factory. Annealing makes brass more durable, so you’ll definitely be able to reload Winchester’s brass if you so please! Non-corrosive Boxer primers cut rust out of the equation altogether.