From Quora: "Although outwardly they look similar they are different rifles. The AK has a long stroke gas system, two locking lugs on the bolt, a simple trigger, is capable of fully automatic fire, and the forearm is attached directly to the barrel. The Dragunov uses a short stroke gas system, a bolt with three locking lugs for greater strength, a semi-automatic only match grade trigger, and a forearm attachment that relieves pressure on the barrel for better accuracy.".
It's chambered in the 7.62x54R (rimmed) cartridge, as is the Mosin-Nagant.