Well, WASR buttstocks are stuffed in there pretty tight, but they will come out.
Be sure to remove BOTH stock screws FIRST. If I remember right, one is under the receiver cover.
I do my "convincing" on the surface that is on the receiver end, the most forward part that is the flat side inside. Put something on this surface like a small block of wood and then pound the stock out against the block of wood with the longest punch you've got. Angle the punch almost parellel to the receiver near where the REMOVED receiver cover should be. I have done this and avoided any damage to the wood. Even if it did ding a little, you wouldn't damage it where it would show.
Take your time and use moderate force...once it moves a little you can work it out the rest of the way by hand.