@ 09:00 am (GMT)
Nathan FosterYou are correct Paul, quite correct, there is no big deal.
The micro changes in OAL are as you say, no more of an effect than changes in wall thickness or temper. We have used the Lee system for many years for precision ammo for ourselves. Steph was going to post that for a number of years, she also made (winning) comp ammo for clients but decided that this thread has already gone on long enough and that she cannot force anyone to understand how or why the system works.
As an example of normal practice, lets say I load 60 rounds for a basic client day tutorial. All cases are trimmed to minimum before hand. The client uses my rifle for say 20 rounds, then switches to another rifle. I have another client arriving next week so I load the 20 cases again. I check the case lengths for safety, but I don't trim. The same thing happens again, and again. Eventually my 60 rounds are all at different lengths. But I will not trim until I am within a C-hair of maximum as I do not have time to p around with this and the rifle is shooting one ragged hole with a low ES when testing it between client visits.
One thing to watch for Andrew, is over analysis during down time when you cannot get to the range. I have seen this effect folk at all levels, from newbies to bench resters. To be sure, if you want to take things to the next level, then you may want to look at flash hole uniforming, neck turning and annealing. However it is more than likely that your rig will shoot very well with basic case prep.
If the case has a burr in the flash hole big enough to effect the lee pin, it is an indication that the flash hole needs uniforming. It is not an indication that you need to use a different trimming system. The flash hole burr needs to be removed. Visual inspection of the flash hole is the first basic step. Trouble aligning the Lee mandrel can be another clue indicating very large burrs. If the burrs are not addressed, they may cause ES and accuracy issues.
Again, do not overthink this. Talking about accuracy and achieving accuracy are two different things. Take note of Marty's comments. Marty will always down play his skills so I will say it- he is a highly qualified and well respected engineer. The way we use our tools is of great importance. We cannot use a cutting lube to aid high speed case cutting as this results in contaminants. So either run your drill at low speed to avoid glazing or cut by hand. The tool is no less accurate than a high end neck turn tool.
This should have been a very straight forwards discussion. Too much time behind computers and not enough time at the range.