i got a promag 30 rd detachable mag for my sks. it fits on fine, but the bolt wont lock open when its empty, and every round gets shoved into the chamber at an angle and jams. am i missing something here? or is this thing just a POS? its not *most* of the time, its 100% stuck every time, scractches the coating off the case it sticks so hard. i havent tried to shoot it yet, if i cant cycle it by hand im not wasting my time at the range in the cold. any thoughts, experience, should i just throw it away and buy a "better" one? what do you guys recommend?