Need help with trimming cases

[paladin]

I'm trying to trim .222 cases down to 1.690" and using a digital caliper to measure them. After some mucking around with the rcbs case trimmer, I got to the point where I thought the cases would be trimmed to that length. I measured the one case I trimmed and got readings of 1.688 up to 1.692. I put the case about 1/4" in from the ends of the calipers blades where the knife edge meets the meatier part of the blade and tried to keep it centered as I did my measurement. As I rotated the case this is where I got the different measurments. What did or what am I doing wrong?? What should I be doing?? Is 1.688 too short a case to use if the trim to length is 1.690?
I don't want to go any further for fear of trimming my cases too short.
Any & all help is greatly appreciated.

 

['Boo]

If the pilot on your trimmer fits your case necks snugly it could be that the problem is your rifle, not the way you are trimming or measuring.

If the bolt face is not exactly 90 degrees to the chamber walls the base of fired cases will show some irregularities as you noticed. It could be the bolt face being being slightly out of square or it could be a misaligned chamber.

In any case rifles that show this usually eat up cases quickly with case head separation in as little as 3 or 4 reloads.

 

['Boo]

Another thought I had is that it could be your press is the culprit. While I have never seen it there is no reason why a press whose die is drastically out of square with the shell holder could bend the case bases to produce the same wobble you describe.

 

[zedex]

When i started reloading i used to place the empty shell in the collet and tighten it down . Then would slide the cutter in place and size the case. But i would have alignment problems. So now i place the case in the collet shell holder and hold the shell in place with the cutter so its aligned perfectly then tighten the shell in the collet. Everything is in perfect alignment and my cases are perfectly trimmed. I wouldnt worry about the .002 shorter cases. Wont make any appreciable difference.