An intermediate rifle
round most commonly used in the most excellent handcrafted blessing
the Avtomat Kalashnikov 47
. It was adopted for use in the AK-47 in 1947. Prior to this the soviets were using Nagant
rifles chambered in 7.62x54r
Being a 7.62mm it has a thirty caliber bullet which it launches at velocities in excess of 2,000 feet per second. While the loose tolerances and rugged construction of its most common launching platform (AK-47) make it very reliable, it does not help much with maintaining accuracy. And it is because of this that it is usually most effective in short range combat. Some less trained people (afghan taliban fighters, somali skinnies) who use AK-47 rifles in combat rely on its capability to spray and dish out damage by their sheer numbers. Note that the round still has enough energy at the 1 kilometer range to fatally wound a human.
Because of production driven by war, there is a huge glut of 7.62x39 surplus ammunition that can be as old as forty years. These military surplus ammunition have corrosive primers and will pit your barrel if you do not clean after every shooting session.
This relatively cheap round, combined with cheap rifles available, although might be neutered semi auto only versions, make it a very excellent choice for anyone who wants a weapon and an easily obtainable stockpile of ammunition for when the SHTF.