This gun was made by the Soviets during WWII. The thing was so popular that it's been used by all sorts of countries. Some still use it today.
Mine was made in 1954. It's got all original parts, including bayonnet, all matching serial numbers. Many different armory marks. One day I hope to know what all the armories are.
The gun is a 7.62x39 chamber, gas operated, semi-auto bolt. Halfway down the barrel is a vent that redirects some of the propellant gasses into a chamber on top of the gun. That chamber contains a piston. When the gasses push against the piston, a rod is pushed out against the bolt, sliding it open, ejecting the spent cartridge, and chambering a new round.
One problem with this arrangement. The bolt has to be driven by a very strong spring to assure that it chambers the new round alright. But since there's no firing pin retractor spring, the firing pin can accidentally slam forward and fire the new round. If that happens, the gun goes fully automatic and you fire the whole 10-round magazine.
Simple solution: file down the firing pin a little. My solution is even easier: fire authentic Russian military ammo. This stuff has an incredibly hard primer. It just doesn't go off on accident.
Once again, this gun has no scope. The front sight is a post in a circular shroud, while the rear is a leaf with click adjustments for 100m increments from 100m to 1km. There's a battlefield setting for 300m.
Now, I'm not trying to say that the gun is accurate to 1km. Certainly, it's not that accurate with me behind the trigger. I don't even know if anyone exists who could fire this thing that well. I'd sure like to meet one, though.