Re: i dont know pressure signs, but...
Make up a feeler tool by straightening out a paper clip and putting a 1/8" right angle bend on its end. Use the tip of the bend to slide in and out along the inside of the sidewall, to see if there are any interior ringlike grooves along the sidewall's interior. If there are, there's a problem, and continued reloading of cases with such a groove can result in case head separation.
Generally, this is an indication that the case is being excessively stretched and re-shortened by resizing, and that the resizing die may be set to resize the case too short, or the load is stretching the case excessively, or maybe both. The die should be set so that the resized case causes a slight bolt drag when closing.
Possibly, the external shiny ring/ridge could be indicating something else/additional. Rebarreling involves a specification called protrusion. The chamber is configured so the case base protrudes a specific amount that corresponds to the bolt face recess. The barrel needs to be seated into the receiver at a specific depth, so the case is supported with minimal interruption.
If a gap exists, the result could look like what you're seeing. If this is the situation, all the cases should exhibit this condition, and an internal groove is likely in all the cases as well, probably even after the first firing. This should be a very rare condition and is almost certainly only going to be an issue with a replaced removed/barrel. This condition should also be detectable using a headspace gauge set.
Greg
