Assault rifle bullet sells out ahead of proposed ban

Sales of assault rifle bullet M855, known popularly as the "green tip" ammo, have sold out in the last couple weeks after the Bureau of Alcohol, Tobacco, Firearms and Explosives announced a proposal to include M855 in its long-standing ban on armor-piercing ammunition.

According to CNNMoney, the ban on the bullets that can pierce vests and body armor is meant to better protect police officers.

The green tip ammo costs about $1 a round, compared to other assault rifle ammo, which can cost anywhere from 30 cents to 80 cents a round. The ammo is commonly used in AR-15 assault rifles.

Read more from CNNMoney.