6ppc neck wall variance

[tenring]

Sized batch of 6ppc brass today, Wilson die, .257 bushing. Cases annealed two firings ago, but did not turn them again. I separated about 20 of the 50 cases, and neck wall thickness varied from .0001 to .0010. The difference was just one ten thou between most of them, but they are all over the place within that bracket. Mitutoyo ball mic. Obviously, neck wall thickness determines bullet tension and they are not all going to be drop dead cookie cutters. So, how much variance in neck wall thickness is acceptable??

 

[j mckinnie]

tenring

the bush size determines tension the thickness variance is going to start the bullet off centre & it will come out off centre.jim

 

[JerrySharrett]

First off, a ball mike is not going to tell you much. Measure about every 45 degrees around the neck with a bullet seated. That is the acid test.

Probably over 0.0003" in concentricity is not going to help nor is it going to build confidence.

Why are you annealing them? After the cases start to split, toss them!!