Here's an interesting tidbit... I just dug out some Hornady .204 brass that has been fired only with the original full-power factory load. Of 15 cases, 12 measure +.003 on the "nominal" length while 3 measure +.002
This creates a great cluster of cases in the +.003/4/5 area, about 23 out of 39 measure in that range. The only other area with more than 2 is the chosen "nominal" measurement.