Just a 0.002" difference is small. I've seen some cases with different loading histories show that much variation coming out of the same die setup. So it seems like you are managing things pretty closely.
If it turns out that 2.810" is both what comes out of the chamber, as fired and is also what you get after resizing with the +0.010 shell holder, as your data seems to show, then what you want to do is go to the next Redding shell holder in the set, the +0.008" shell holder, to see if you start moving your 2.810" shoulders back to 2.808". That would constitute a -0.002 "bump" and will be a good brass-working minimum.
Here's an alternative explanation to what you are seeing:
You are getting essentially the same dimensions for both new commercial ammo and your resized cases. It is not unusual for a once-fired case to let you close a bolt freely because it normally springs back a couple of thousandths in length after firing. You would have to neck size it and refire it several times before it really filled the chamber size completely. But what it unusual is you have proven you are resizing the sides of the case. Doing that lengthens the head-to-shoulder dimension by squeezing the case narrower and longer. Then the shoulder in the sizing die makes contact and extrudes the shoulder back.
Since you are not seeing a case come out longer than 2.810", I think your die is meeting the case shoulder. And since that resizing is returning you to the new cartridge case size, it suggests your chamber is actually at the SAAMI minimum or very close to it now and that what is tripping you up is that your resizing die is on the short side or your +0.010" shell holder is mislabeled.
Let's prove this one way or the other. First, take your 0.000 shell holder and the +0.010" shell holder and measure both with your caliper. The latter one should be ten thousandths longer. If it isn't, you want to make an actual deck height measurement with the depth probe that sticks out of the back of the caliper beam to measure from the top of the deck to wher the case head rests. Sticking a feeler gauge in gives you a good way to rest something on the case head surface and then measure to the feeler gauge. Add the feeler gauge thickness to your calibper reading and the +0.000 shell holder should giver you 0.125" and the +0.010" holder should give you 0.135" deck height.
If all that checks out, do what I suggested and go to a +0.008" shell holder and see if you don't get your cases to shorten another -0.002 so you no longer have any 2.810" cases. All 2.808" or so. If that works, it makes it look like the die is a little short.
Another test you can make is to set the feeler gauge on top of one side of the shell holder deck and resize a fired case, stopping on the feeler gauge. When you measure the head to the shoulder, it should be longer than 2.810" because of being squeezed narrower along the sides, and this will confirm that the shoulder of the die is pushing it back which would confirm the die is short.
Finally, you can sacrifice one case (I would just clean a range pickup for this) by resizing it with the +0.000 shell holder to confirm it gets too short.
Let us know what happens? If the die is short, I'm sure Redding will make it right, if you need them too.
If it turns out that 2.810" is both what comes out of the chamber, as fired and is also what you get after resizing with the +0.010 shell holder, as your data seems to show, then what you want to do is go to the next Redding shell holder in the set, the +0.008" shell holder, to see if you start moving your 2.810" shoulders back to 2.808". That would constitute a -0.002 "bump" and will be a good brass-working minimum.
Here's an alternative explanation to what you are seeing:
You are getting essentially the same dimensions for both new commercial ammo and your resized cases. It is not unusual for a once-fired case to let you close a bolt freely because it normally springs back a couple of thousandths in length after firing. You would have to neck size it and refire it several times before it really filled the chamber size completely. But what it unusual is you have proven you are resizing the sides of the case. Doing that lengthens the head-to-shoulder dimension by squeezing the case narrower and longer. Then the shoulder in the sizing die makes contact and extrudes the shoulder back.
Since you are not seeing a case come out longer than 2.810", I think your die is meeting the case shoulder. And since that resizing is returning you to the new cartridge case size, it suggests your chamber is actually at the SAAMI minimum or very close to it now and that what is tripping you up is that your resizing die is on the short side or your +0.010" shell holder is mislabeled.
Let's prove this one way or the other. First, take your 0.000 shell holder and the +0.010" shell holder and measure both with your caliper. The latter one should be ten thousandths longer. If it isn't, you want to make an actual deck height measurement with the depth probe that sticks out of the back of the caliper beam to measure from the top of the deck to wher the case head rests. Sticking a feeler gauge in gives you a good way to rest something on the case head surface and then measure to the feeler gauge. Add the feeler gauge thickness to your calibper reading and the +0.000 shell holder should giver you 0.125" and the +0.010" holder should give you 0.135" deck height.
If all that checks out, do what I suggested and go to a +0.008" shell holder and see if you don't get your cases to shorten another -0.002 so you no longer have any 2.810" cases. All 2.808" or so. If that works, it makes it look like the die is a little short.
Another test you can make is to set the feeler gauge on top of one side of the shell holder deck and resize a fired case, stopping on the feeler gauge. When you measure the head to the shoulder, it should be longer than 2.810" because of being squeezed narrower along the sides, and this will confirm that the shoulder of the die is pushing it back which would confirm the die is short.
Finally, you can sacrifice one case (I would just clean a range pickup for this) by resizing it with the +0.000 shell holder to confirm it gets too short.
Let us know what happens? If the die is short, I'm sure Redding will make it right, if you need them too.
