Are you sure it's not a measurement issue? If you mark a vertical line on case shoulders with a sharpie and also mark the shoulder insert thingy as well. Measure a case with the marks lined up then size and measure again with the marks lined up. Try a few cases are you still seeing the same variation? when you sit the case in the callipers/gauge wriggle the base of the case side to side along the axis of the blade of the calliper to seat it, while applying gentle pressure. I found one of these really tightened up my measurements https://benchrite.com/davidson-seati...-checker-base/ I got it from Sinclairs
I also agree with beetroot, as long as you check for imminent case head separation with a hook-shaped probe inside the case and they are all good and they all chamber, eject cleanly after firing and shoot ok then I wouldn't worry.
Last edited by yerimaginaryM8; 04-09-2021 at 09:30 PM.
So I think I've solved the mystery. I thought is was just my non-annealed cases so I got them annealed and the inconsistencies persisted. My next thought was it must be the play in the press turret, a nice new single stage didn't help (no, I didn't buy one). Then at some point I stumbled across several references to this video. All my cases with the exception of 1 came out with a variance of 0.001". I'll check it over some more resizing, but I'm getting ready to hang up the calipers.
180deg? try 90deg, then maybe 90deg again. Works well with neck sizing, may work with full resizing and shoulder bumping?
Guys... just a small trick on using calipers...
There is always a little slack along the green line pictured below.... varies from one to the other.
First, ensure the springs along the green line are in good nick and keep the bottom slide of the car body firm against the bottom of the rail.
Then instead of using the thumb wheel or thumb on the position in the black circle.... just exert a little light pressure to "hold" the case, either side of the lower jaw adjacent to the case... red arrows... this prevents the spring(s) on the slide at the green line from compressing which in turn results in more consistent readings.
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