Breivik can be seen with the Ruger Mini-14 in the end pages of the manifesto. Breivik reportedly said of the semi-automatic gun, "this is the most military-like gun that is allowed in Norway."
In the picture above Breivik holds the Ruger Mini-14, which can accept high-capacity magazines of up to 30 rounds. Breivik also legally obtained a Glock 17, which comes standard with a high-capacity magazine.
Under Federal Assault Weapons Ban in place in the United States between 1994 and 2004, magazines of greater than ten rounds were banned. But as in Norway, they are currently legal in the United States.