I would be looking at the rails see if one got bent.
was it a factory mak-90 or one built from a kit? I had a tantal on a receiver built from a flat that would do that. took a rubber mallet to unstick it. replaced receiver with a quality one, and problem gone.
there really isnt much in there that could stick it up unless something broke or got bent.
you could also check the lugs on the bolt and the barrel. if something is clogging them up, that could lock it too, but thats kinda unlikely. would have to be something big, like a piece of thick metal.
after reading your post again, look to see that your bolt carrier is moving on the rails. if one side jumped a rail, or both are on top of the rail, it will lock up too. there is a notch in the carrier that the receiver rail is supposed to run through. with the cover on, you cant see this. the gas piston will keep things moving in the right direction. if the carrier is not on the rails correctly, the bolt cant go into battery since the closer the carrier gets to the barrel, the more friction builds. If this is what is happening, dont cock it anymore til the carrier is riding correctly or you could bend your rails.
I have seen rifles where the cut that allows the carrier to be lowered onto the rails was too far forward allowing the carrier to jump the rails at random.
RIP Mark 1977-2005 I miss the hell outta you bro.
Happiness is a warm AK
If guns cause crime, all of mine are defective."
Last edited by kf4zra; 04-03-2010 at 22:39..
Reason: added more.