6BR FL sizing dimensions not making sense, need assist

[Linko]

I am resing my first 6BR Norma brass and am finding a problem when I check with a LE Wilson case gauge.


Here is what equipment I am using:
Forster co-ax press
Whidden FL die
Whidden case gauge
Whidden caliper shoulder datum collar
LE Wilson case gauge

I have some factory Lapua loaded ammo that I fired. I fired then cleaned and deprimed some rounds. I measured with both the Whidden case gauge and the shoulder datum collar on my caliper, before and after resizing.
Here is the results:
Before sizing,
w/ caliper = 2.130 w/case gauge = .002
after sizing,
w/caliper = 2.127 w/ case gauge = .000

here is where I have the issue. the above would be a setback of approx .002 so far so good. when I slipped the resized round in the wilson gauge to double check. the case head is a fingernail high on
the gauge (headspace). geeze, so I took a fresh loaded Lapua round and pulled the bullet out to measure the factory brass.
Here are those measurements:
w/ caliper = 2.126 w/ case gauge = (-).001
now i measure the factory (unfired) case in the Wilson gauge and the head is perfect, below the no go surface of the gauge. that is strange. so I resized a case to match the factory case dimensions and check it in the wilson gauge and it is still no-go, slightly high to the gauge surface!!!!

please help me figure what I am doing wrong. thanks

 

[KRP]

I'd say it's not the shoulder causing your "problem", measure the rest of the case. How do go/no go gauges measure in that tool? Do cases chamber and function in the rifle?

 

[Patch700]

Any particular reason why you are sizing your brass to accomadate Wilsons case gauge and not your actual rifle?

Why not partial size a case 2x fired and then measure head to datum. Then you will have a concrete # as to the length of your chamber and therefore would have a base number to how much to bump back from.

You can make a square peg fit in a round hole and vice versa but the fit will be less than stellar.

 

[potatoe]

http://forum.accurateshooter.com/threads/bumping-the-shoulder-001.3890889/#post-36677937

leaf thru this thread.

 

[BoydAllen]

Stick with your Whidden gauge, load a case say tree times, neck sized, with a safe but stout load. Knock out the primer measure it with your Whidden gauge, and record the number, including interpolation. Set your die up to bump the shoulder back .001 or so from that number. Check the sized case in your rifle. If the bolt does not close in a satisfactory manner, get a smaller die. Put your other gauges aside. Stick with one. The Wilson is not as precise.

 

[Linko]

I did further measurements. I measured the case dimension at the case head end and it is .470 on the resized brass and .467 on the factory case. so thats why it isnt fitting in the wilson gauge.

I will stick with the Whidden and tomorrow test fit some unsized and resized cases in my rifle chamber. to see how they chamber.

I dont have a neck sizing die so I will see if the unsized cases load in my chamber and if the unsized fit I could reload unsized on the high end of the powder and check the dimensions after a second firing. how does that sound?

thanks