Thread: Prepping new brass ?

So GrandpaMac and Oldbloke, I've acquired a couple of hundred brand new, primed, Winchester Super cases in 22 Hornet. The Hornady reloading book states: Maximum Case Length 1.403, Case Trim Length 1.393. A random selection on the new brass measure; 1.399, 1.401, 1.402, 1.404, so I'm guessing I should be trimming (and de-burring) the whole lot back to 1.393 for consistency. I'm trimming all the fired brass back to 1.393, and batching by brand and age as best I can. Some are mixed up purchases. Firstly, I'm surprised that newly manufactured brass have that much variation in length? Secondly, how much is accuracy affected (within one batch at 100 metres) by having variable case lengths?