hey everyone, this is my first post and sorry it has to be a question. i was following the instructions in the owner's manual for diassembly and got to the point of pulling r.s.t. toward muzzle, rotate 1/4, then let slide into receiver. well, mine doesn't slide into the receiver, it looks as though the pointy ears on that plastic piece won't let it slide through the arch. what am i doing wrong here?