"I ensured all the cases measured 2.476" "In the beginning..."? The case length was 2.494 - a few, before you trimmed the case .018 + or minus it was/is recommended the case be trimmed to 'trim to length', for most cases that would be .010 thousands below max. length, then there the thought cases get longer when fired,, not always so, I have cases that shorten .040 thousands, as in chambering a case that is 2.494 long and fire it, when ejecting the case I find the case shortened .040 thousands, rational: DIFFERENCE, difference in the size of the chamber and the size of the case, before the case gets longer when fired for the first time, it gets shorter when the case fills the chamber, but that is a hard sale to a reloader because to most reloaders "TIME IS NOT A FACTOR" and then there is that fuzzy area of stretch and or flow and bump. BUMP? ME? I wreck-um.
Reloaders and bad habits: I could mindlessly pill the handle, raise the ram and size cases all day for a chamber I do not have, so I determine head space first as in determining the effect the chamber will have on the case when fired, by knowing the difference between the size of the chamber and sized case, when I have an option, I can size the case to off set the effect the chamber will have on the case when fired. AGAIN, I have M1917 with .016 thousands head space, scary stuff? NO! I add .014 thousands to the length of the case from the head of the case to it's shoulder "THEN' add .014 thousands to the length of the case, that leaves me with a case that is 2.508, that number does not exist in any reloading book of specifications.
For me there is no advantage to short cases, I want my cases to cover the chamber, again my favorite die is the case forming/trim die, with little effort I form cases that can be used to determine the length of the chamber from the bolt face to the throat of the chamber, and to me there is no such thing as bump, I wreck-um, I erase the shoulder and reform it as in part of the shoulder becomes part of the case body and part of the neck becomes part of the shoulder. The neck does not get bumped it is erased.
The instructions for the 'X' RCBS die is trim the case .020 thousands below maximum length and then it goes into rational, the rational goes on to say by the time the case gets too long? the case will stabilize, then in the other world of reloading it is said cases harden after 5 firings and 'little useful information can be gained from the fired case for the effect of pressure, and then the part about neck sizing 5 times after the first firing, THEN, full length size the case to start over, HOW? The case has been fired 6 times.
My favorite cases, cases fired in trashy ol' chambers
Wreck, rectify = change, bump sounds like an accident unless you are shipping on the seas near Main, New Hampshire and Massachusetts, then it become 'stove'.
F. Guffey