A brief note on slamfire problems- the SKS uses a floating firing pin- free to rattle back and forth. When cosmoline that has dried and hardened for 40 years gunks it up, and it is stuck in the forward position, chambering a round and letting bolt slam forward makes it fire- safety or no safety- hammer never fell. It will empty the mag unless firing pin unsticks itself. Not urban legend- have been involved in shooting case whee this happened.
Cure- clean the firing pin channel, be sure pin can move, and have muzzle pointed in safe direction when chambering a round. For first shooting of a NEW to you gun, onlly load 2-3 rounds- if it goes full auto, limits the WHOOPSY factor.
There has been discussion about adding a firing pin spring to these, but mine work fine when kept clean. Have had one since 1968.
What we have here is... failure- to communicate.