Neck thickness seems logical. So my 37 fire formed cases could have differing measurements on Hornady Headspace Comparator due to neck thickness variances on these Hornady cases?
Sorry, yes, case lube for resizing brass. I also use q-tip to put some inside neck when resizing. Do you use graphite inside of neck for bullet seating?
I media tumble again after resizing to remove all lube and try to remember to swab necks with clean patch to remove any media residue stuck in there. I do this because I may not tumble for the same time every usage and want to remove any excess carbon from the neck too. I personally try and keep my necks as uniform as possible. Both in cleanliness and in measurement. I personally believe variation in neck tension is the biggest culprit for unexplained flyers when shooting for groups on paper. Regardless of the cause of the variation.
Annealing is next on my to-do list but I'm just not going to try to do it manually by hand. Worried about not being able anneal perfectly the same if I try and count in my head while torching the brass. Also, If I ever get into bolt action long range shooting I plan on buying an arbor press that uses a bullet seating die with a dial indicator to measure seating force.
I've never used any lube to seat bullets, I just know that some do.
I don't have a 6.8, but don't expect any variation in case neck thickness to show up in headspace variation. It's normal to see a thousandth or so variation when checking fired cases. Particularly if the brass is new or only has a firing or two on it. Some cases need to be fired and re-sized a couple of times before they reach their full expansion due to "spring back". I wouldn't sweat this and just set size die to accommodate longest measurement from few random case measured.
I have found that ogive to base measurement never is perfect for me. In addition to everything we've talked about here, your bullets themselves can even be the culprit even if you have perfect cases to start with. Take that same comparitor and measure some of the bullets by themselves and see if you have any variation. I measured a box of Hornady 120 SST's and found they varied by a couple thou. Most were dead on and I love that bullet in another cartridge.
I try and fine tune my load in .005" OAL increments after finding the powder charge instead of just loading to magazine length. Obviously, the only direction away from magazine length you can go is shorter OAL.
For load development if I notice handle pressure variation or if I have a round with a OAL that's a good bit off from the rest I set those aside so I don't risk a preventable flyer from showing up on paper.
For hunting, I shoot them all as they come off the press regardless of OAL variation whatever the cause because it really won't matter much at 100 yard hunting distances.
