Most people reading this will probably say "Duh, are you just now figuring this out", but the answer is yes I am just now figuring this out. So to my understanding as a case is fired throughout its life the same bushing will have different effects on it due to the spring back quality. This will lead to a gradual decrease in neck tension as it is fired and sized again. I have been finding that my cases that have been fired 5 or 6 times, I can tell a big difference in the seating effort. I think that the lower neck tension is helping my groups. Do you guys step down your bushing size at different points in a case life? If you do does it seem that about every 5 firings a bushing .001 smaller is needed? I guess the best way to know is use a mic to take readings at different points to check the tension.