That's not exactly abnormal variation in seating depth. Those bullets' profiles may not match very well with the seating stem in the dies you're using. Even if it does, ogive lengths vary. For that matter, there may be some of that sort of mismatch or variation in your measuring tool (not that there is, but most people don't check that sort of thing or don't have tools or methods to do so). Runout is one thing, a couple thousandths of seating depth variation is another. I'd investigate, but I wouldn't lose too much sleep over this.
