Picked up a Yugo M90 RPK in 7.62x39. Very awesome to add to my collection of Yugo's and now my collection is complete for as far as I want to take it. However, my Yugo RPK detent pin for the muzzle nut, won't retract. Basically it doesn't move backward at all. No signs of tack welds or anything, the pin just won't move. FYI- these RPK's are awesome, they even have a quick detach bi-pod.