it may be that the case heads are not square Stix
another can of worms mate
very sorry
its something that not many people worry about or know about
https://www.longrangehunting.com/thread ... ring.9866/https://www.shootersforum.com/handloadi ... heads.htmll do square the case heads of my cases that the action has been worked, the bolt has been squared to the chamber ect...
now to explain my theory
when squaring the case heads you see that on most of these case's there is not a lot of the case head actually touching the bolt face
usually l find its only a ring around the primer hole raised up like a mound or the case head is lopsided ect..
but there are only a few out of say 100 that will contact more than 75% going by the cut on the case head,
expensive cases are affected no different to the cheaper cases
so when you are measuring headspace you may be measuring the high part off the case head that does not get touched when sizing because there is a hole in the shell holder
you may be able to check this by holding different cases up to a light to see if you can see light through a gap when measuring, some say this is corrected by shooting your cases so they fireform to your chamber at the casehead as well as the body, its also said that an action that is not trued with the bolt face true to the bore wont make any difference, l dunno
but if it is true that when you fireform your cases the case head is flattening out on the bolt face it isn't really a problem after you fireform
these cases were fireformed before the case heads were trimmed and l only took off the humps around the primer pocket,
you can see they are not lopsided like some are
l'm only saying this may be the cause of inconsistent readings not that its another step everyone should do
hows that for OCD micro (anal)
makes me happy
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