7.62xfun is correct.
Also, it is a takedown version. If you find there is play between the barrel section and the receiver there is an adjustment to correct that (if it isn't already maxxed out).
The milsurp version described above was called a trench gun or trench sweeper. They are famous for their 'firehose' mode. You can hold down the trigger and just pump new cartridges in and it will fire each time.