I purchased a used XD 40 at a Local Pawn shop the other day and immediately took it out and fired around 100 rds through it. I fired the first hundred rounds with no problems and decided to call it a night because it got dark. The next morning I took the gun out to a local range and fired around 20 rds when the rounds wouldn't seat in the chamber. I would fire off a few and then it would cease up with a round half way in the chamber. All I had to do was pull back on the slide a little bit and the bullet would seat and go forward. I didn't lube the gun up before taking it out or clean it after the first hundred rounds becuase it didn't appear to need it at the time... could this have caused the problem or might it be part of the internals? This is my first hand gun so i really can't tell what it could be. Also, the problem didn't persist for the last 40 rds or so I fired.