I was having trouble with occasional FTFs and I was wondering if it was the Tapco mag I was using. Then I happened to notice something between the original receiver cover and the aftermarket one. For one, the aftermarket is thicker in the back causing the spring to have more tension than it should. Also there seems to be some minor denting in the back leading me to believe that the metal is too soft. Lastly, that the spring actually sits up HIGHER in the aftermarket receiver cover that I am using than in the original. When I used the original receiver cover, my Yugo SKS ran flawlessly. Maybe I could machine fix some things in the aftermarket receiver cover, but the question would be whether or not it would be worth it? Naw. If you HAVE to put a scope on your SKS, just drill tap it to the receiver. I'm not doing that, but that's the recommendation. Thanks guys!