Case Trimming Question

[flowrie]

Have a question. Have an RCBS case trimmer which was not very repeatable, so I purchased an LE Wilson case trimmer. The LE Wilson is superb, I like it a lot! So I deprimed some 6.5 Creedmore, cleaned, tumbled, flash hole and primer pocket prepped, and then performed a full length resize ( for a MSR, not a bolt gun). All the normal stuff, then I trimmed the cases on the LE Wilson. They all measured exactly 1.910. I actually enjoy trimming cases with the LE Wilson. After trimming I then chamfered and deburred and then set aside. A couple of days later I measured the cases again. I just wanted to admire my handiwork again after using the Wilson trimmer. Darn it, those cases now measured 1.912 to 1.916. What is going on?
BTW, I did trim them back to 1.910, but have not chamfered or deburred again.
What am I doing incorrectly?

Thanks in advance!

[mrvmax]

I'd say it's your measuring device, accuracy to thousandths is not great. You can change the reading by just holding them tighter too, even with Mitutoyu or Starrett. Leave them as is.

[flowrie]

I'd say it's your measuring device, accuracy to thousandths is not great. You can change the reading by just holding them tighter too, even with Mitutoyu or Starrett. Leave them as is.

I kinda doubt it was the measuring device. I say this because the Wilson trimmer was still setup for 1.910 and when I trimmed again a small amount of material was removed from the casings. Could it be temperature change? Could the chamfer and de-burr after the initial trimming somehow caused a burr on the case mouths? Could the brass spring back a little in length over time (a couple of days)?

[mrvmax]

I'd say it's your measuring device, accuracy to thousandths is not great. You can change the reading by just holding them tighter too, even with Mitutoyu or Starrett. Leave them as is.

I kinda doubt it was the measuring device. I say this because the Wilson trimmer was still setup for 1.910 and when I trimmed again a small amount of material was removed from the casings. Could it be temperature change? Could the chamfer and de-burr after the initial trimming somehow caused a burr on the case mouths? Could the brass spring back a little in length over time (a couple of days)?

I use the Wilson too and have never seen that. But, I never go back and recheck either. I doubt you had enough temp difference to do that.

https://van.physics.illinois.edu/qa/lis ... mperatures