A 12 Gauge Frag round is designed to burst on impact, littering the target area with shrapnel. Frag rounds are currently being considered for military use.
Battlefield Bad Company 2
In Battlefield: Bad Company 2's singleplayer, 12G Frag rounds can be found on the collectable TOZ-194 when equipped with slugs. It is the only shotgun in singleplayer to use the 12G Frag. In multiplayer, DICE employees had access to 12G Frag rounds, nicknamed "DICE-BOOM". The round caused large craters comparable in effect to C4. This has only been seen in use on modded servers possibly meaning it was part of a test for 12G Frag rounds to be added via patch.
— Battlelog description
In Battlefield 3, the 12 Gauge Frag round is an advanced ammunition type used for shotguns. The explosions generated on impact increase potential Suppression, but also sacrifices accuracy and stopping power.
The frag rounds explode on impact, causing a grouping of several small explosions on target. In Multiplayer, this not only suppresses the enemy, but also leaves the opposing player in disarray as it is difficult for them to ascertain the direction of incoming fire. Players not under fire from the frag rounds however, can easily locate the shooter, as Frag Rounds produce a very large tracer, almost akin to that of the IFV main gun.
The addition of slight splash damage makes these rounds very effective for suppressing and killing grouped enemies, or enemies popping in and out of cover. It is also possible to kill enemies just behind cover by shooting the floor by them due to the splash damage. One example of this is on Seine Crossing, along the alley between the RU Deployment and Back Streets, where the splash damage and spread can be very useful. Two direct hits from frag rounds will kill an enemy in Normal mode at any range, although at range the spread of the rounds makes it hard to pull off a kill, as well as the fact that frag rounds are some of the slowest traveling rounds in the game.
The blast damage from frag rounds can kill the user if shot on the ground or a wall close to them. Three explosions will kill a player at 100% health, and the death will be considered a suicide.
Frag rounds also have the ability to damage armored vehicles, including IFVs and MBTs. The blasts can penetrate through the windows on light armored vehicles such as the HMMWV.
The December 6 2011 patch reduced the damage done by 12g Frag ammo when fired from semi-automatic shotguns. A separate patch reduced the rate of fire of the USAS-12 and MK3A1 when equipped with 12g Frag rounds.