non-concentric case neck on fired case.

[passion4shootin]

Hi all,

Need a little feedback on a finding.

Rifle is a custom 6.5 - 284 (0.288nk)
case is a nosler custom with neck turned .0105 - .0107 thickness.
loaded neck dia is 0.2855
Bullet is a Berger 140 VLD seated at COAL 2.500

Jammed COAL is 2.563 ( just measured ). None of the loaded shells were jammed.

What I noticed is that about 60 - 70% of my fired case has a run-out of 0.002 - 0.004
measured around the neck. The same case when measured at the web and right before the
shoulder shows a perfectly concentric case.

The rest of the case will mic out to 0.001 run-out and seldom ( 3 0f 50 cases ) less than 0.001 .

What could be the cause of the case neck getting out of whack?

Thanks in advance for any insight.

 

[Larry Elliott]

I presume that the runout of the necks is before sizing, and the only thing that jumps out at me is that the chamber wasn't reamed in line with the bore and/or the neck of the chamber was cut with a neck reamer that wasn't lined up properly. If I'm wrong, which frequently happens I'm sure I'll be told I'm nuts. No problem, I am.