My ND was also with a SKS that I bought in college. For $100 I got the rifle and for another $40 came all the cool accessories like the folding stock and 30 round removable magazine. That magazine was the problem. After blasting away with the cheap russian ammo, my brother took the magazine out to reload and I decided to sight it in with some US made softpoint rounds. He had just handed the rifle to me with the bolt locked back and magazine removed when I dropped a single in the chamber. When I pulled the bolt back and released, a smoking crater suddenly appeared 2 feet from my toes and about 6 inches from his heal.
I guess the increased bolt velocity allowed the firing pin to set off the softer commercial primer. After checking out pants for residual matter,
we tried to recreate the incident and about one in five Federal 123 soft points would fire but the steel cased russian stuff was fine. Lesson learned: be careful with guns from nations that have lots of expendable soldiers!