I have received carbines over the years that had soot so hard the plunger could not move all the way back. This causes the pointed end to get beat down and does not hold the extractor as will as it should. I got one with the plunger so beat up it was turned sideways about to come out. I have also received carbines with the plunger in backwards.
I also recevied one with a garand plunger and spring in it. At first I thought I had found a new design. What a laugh I had when I was told the part was for a Garandicon.