Recently acquired the RCBS MIC to check case length and set shoulder bump. Previously I was using a Hornady Comparator and the 30 cal. insert, figuring that would get me close enough to the datum line.

Here's my head scratcher.
Lake City brass, full length sized in a Lee die, twice fired in the same gun, last firing was all with the same load. Rifle was an AR, Wylde chamber.
MIC readings vary from +.004" to -.003", or .007" total variance.
Is this a normal variance? Seems wide to me. Most were between +.001" and +.003".

Set the Redding bump die to get zero on the MIC and call it good?

No opinions? Odd for the Fire.

Maybe I should add Trump to the subject line.

I use a precision mic for most bottleneck cartridges, and have found them to be pretty accurate for that.

Are you screwing them against the shoulder with the same torque, that could make a difference.

You mentioned twice fired in the same rifle, how many times total? It could be time to anneal to restore consistency.

Are the rims straight? I've had loads on the warmish side kinda pull on the rims, and that would affect the reading.

Thanks for the reply Vic,




Thanks,
NVhntr

Oh, I forgot....are you voting for Trump?....(grin)


Sounds like you have a handle on it. Usually when I see inconsistency it's time to anneal.