The 12 Gauge Buckshot is a common load of shotgun shell, composed of seven to nine 00 "double-ought" steel pellets.
The 12 Gauge Buckshot is the default ammunition for all shotguns in Battlefield 3. It inflicts the most damage against infantry (often a one-hit kill), but only at close range. In addition, 40mm grenades from the M320 grenade launcher can be loaded with buckshot.
Although the stopping power of the 40mm buckshot is high, it isn't recommended for use due to its low rate of fire. The M26 MASS is better suited for close range due to its higher rate of fire and similar amount of damage.
— Battlelog description
12 Gauge Buckshot is a shotgun ammunition type in Battlefield 4.
It is the default ammo for all shotguns, except for the USAS-12 Battle Pickup. It inflicts very high damage at close range, often a one-hit-kill, but its effectiveness is limited over range, due to its fast drop-off and low minimum damage.
Unlike normal bullets or flechettes, its pellets cannot reliably penetrate materials such as plywood or sheet metal.