Thread: Case lengthening when bump sizing

Originally Posted by ebf

All of these issues can be identified and correct by doing the appropriate measurement.



I don't really agree with this BW. The case may well have been sized correctly, but during that process, brass flowed into the neck causing that to get longer. The shoulder and other case dimensions may well all be within spec.

Couple of suggestions from my side:

If you want to measure sizing in relation to the shoulder (i.e. bump), use the correct size bump gauge to measure the datum line.

To see if you need to trim, measure overall case length AFTER resizing. (@Dermastor) If you don't think cases stretch during resizing, simply measure the case BEFORE and again AFTER. DO multiple measurements, and make sure the flat part of the vernier blade is seated well in the case.

I wasn't disagreeing that cases can stretch, we all know they do. I was meaning that if a case won't chamber, the shoulder hasn't been sized enough. Cases don't datum on the neck, they headspace on the shoulder, a neck can be a fraction too long and does not prevent chambering. If the shoulder dimension is 'in spec' with the chamber it will fit in chamber, it its not 'in spec' it won't fit in the chamber, regardless of the neck. I thought this was fact as far as case an chamber specifications go.
Only in an extreme case that a neck is excessively long it may prevent chambering, but we weren't talking about extreme excess.