5.56mm round

The 5.56mm Round is a type of small guns ammunition found in Fallout 3 and Fallout Tactics.

Fallout 3
Generally speaking, the 5.56mm Round is the third most common small guns ammunition found in the game, behind .32 Caliber Round and 10mm Round. After The Waters of Life it becomes much more available as enemies start carrying the Assault Rifle in place of the Hunting Rifle. The 5.56 appears in sickle clips across the wasteland.

Equipment
If difficulty is experienced when trying to find enough 5.56 ammunition; there is a relatively easy way to acquire it. Brotherhood Outcast Casdin (found at Fort Independence, South of Vault 101) will allow you to turn in various items of technological value for; tons of 5.56 ammo, Stimpaks, grenades, or Rad Away. Casdin's subtitles incorrectly call it ".556 ammo". Prolonged trading with the Outcasts will also eventually gain you access into Fort Independence without the residents becoming hostile.


 * Note: After you've visited Canterbury Commons, and invested in the weapons and armor merchants (Lucky Harith and Crow), they will start selling power armors and laser weapons. These are usually in poor condition, and as such they are very cheap. Fast travel to Fort Independence and trade for ammunition. Sleep 48hrs, rinse and repeat. Using this method you can build up thousands of rounds of 5.56 quickly and cheaply. Additionally, Chief Gustavo of Tenpenny Towers usually has cheap laser rifles and pistols.

Ammo
Weapons using 5.56mm ammunition:
 * Assault Rifle
 * Chinese Assault Rifle
 * Xuanlong Assault Rifle

Fallout Tactics
Weapons using 5.56mm ammunition:
 * M16A1
 * Ruger AC556F