I think the OP is talking about the slight step in the case closer to the head. There is a very minor one visible in your picture, just above the lowest (open center) spot of tarnish. It indicates how far down the sizing operation actually was done on the case.
What you are talking about is the visible step in the case where the bullet's base sits, because the bullet has expanded the case a little when it was seated.
What you are talking about should not affect chambering in any gun. What the OP is asking about MIGHT affect chambering if the case was previously fired in a gun with a large chamber, reloaded, and used in a gun with a significantly tighter chamber.
Last edited by SL1; September 10, 2012 at 03:59 PM.