Andrew, Thanks for the excellent information. I'll measure a bunch of fired cases this evening to see what the average case capacity is. I downloaded and read (twice) Chris Long's paper on shock wave theory. I also downloaded his OBT Excel tool. Once I get an accurate case capacity I sure hope that N540 is still a good powder to use. I chose it based on Barnes' manual which has N540 loads for the 235gr and 270gr TSX bullets. Thanks again. eastbank, That's awesome!!