HK53

The HK53 is a carbine made by German firearms manufacturer Heckler & Koch. It is a variant of the HK33 assault rifle, and operates on the same principal as the G3 battle rifle and the MP5 submachine gun, but it is chambered in the 5.56x45mm NATO round and is fed from 30-round box magazines. It is featured in Battlefield 2: Euro Force, Battlefield Play4free and Battlefield 3: Back to Karkand.

Battlefield 2: Euro Force
The HK53A3 is the standard carbine issued to the EU Special Forces kit in Battlefield 2: Euro Force. It has moderate firepower, low recoil, and a decent rate of fire. It comes with a 40-round magazine, and can be fired either full-auto or in mechanical bursts, though there is no difference in terms of accuracy between the two.

Battlefield Play4Free
"The G53 is actually compact assault rifle design based on it's well known bigger brother, the G3 assault rifle design. It is chambered to fire the 5.56x45mm rounds giving it outstanding stopping power and reliable accuracy for a weapon of it's size making it a perfect companion for the Engineers who like to hit the front lines hard."

- Battlefield Play4Free Announcement

The G53 is a primary weapon for the Engineer kit.

Battlefield 3
The G53 is a weapon added in Battlefield 3: Back to Karkand expansion pack. It features three-round burst, full, and semi-automatic fire modes, a moderate rate of fire, moderate damage, and a 30-round magazine capacity with four reserve magazines by default. It is unlocked when the player completes the Assignment "Fixing It" which consists of:
 * Performing 10 repairs
 * Killing 1 enemy using the Repair tool

Trivia

 * The G53 in Battlefield 3 was originally only called the HK53 on the PS3 version, but its in designation was changed after a patch from HK53 to G53 like the other platforms.
 * In Battlefield 3 the HK53's receiver clearly has a fire selector for a 2 round burst mode but when selected in-game it fires in 3 round bursts.
 * In Scavenger, the G53 can be found with both a suppressor and a laser sight, a combination not normally obtainable, as both share the same attachment slot.
 * If you have Battlefield Premium and Battlefield 3: Endgame, the Navy Blue Digital Camoflage and the Woodland Stripe Camoflage can be unlocked for the G53/HK53 by completing the G53 Specialist assignment.