Re: New vs. Once fired brass questions
One other tid bit of maybe or maybe not useful info is that if staying within one <span style="font-style: italic">brand</span> of brass, ie headstamp, lot number really is a non issue if the load is worked up properly with OCW protocol.
We're dealing with a rapid internal combustion taking place that creates an amount of pressure/force to drive a bullet down a barrel, and then to some point down range. The amount of space this combustion has to burn in dictates the behavior of the force that drives on the bullet. One limiting factor of this space is obviously the internal capacity of the brass. When this internal capacity is close from round to round then we get a more a consistant burn and more consistant behavior of the driving force, and a more consistant impact point down range. This is why some of us say to not mix headstamps as the internal case capacities can and do vary between makers.....most times enough to change the load enough to get very different results. Sometimes dangereously so if you are not paying attention to details.
When dealing with a brass from the same maker, finding the center of a node with the OCW principles give you a range above and below that center, of consectutive powder weights, usually a grains worth or so total, sometimes more, that all offer the same behavior down range. This range of powder weights translates into a range of different pressure levels that all do the same thing. This range of pressure levels that are incorporated into the load by default are usually enough to override any miniscule difference in case capacity within the same headstamp.
If you understand OCW then you understand "accuracy" is not necessarily a function of exact speed, but rather a function of timing the exit of the bullet from the muzzle of the barrel at the most opportune time, by addressing issues with barrel harmonics. For this reason I gave up worrying about maintaining the exact lot number for the whole inventory of my brass, and gave up weight sorting my brass as a waste of time. I do not though, as a matter of religion, mix headstamps.
Was any of that mean?