Would this concern you. I have a few random dark areas on cases that don't seem to clean up readily.

That looks almost like gas lealing out a fracture in the case, try putting the case in your mouth and sucking on it like you did as a kid, plug the case mouth with your toung and seeing if it will hold a vacuum.

Excellent advice from Bob.

By the way, don't shoot them anymore. The gas escaping at the split can work like a miniature cutting torch and damage your chamber.

If you begin noticing an extruded "dimple" on your cases at the same distance up the case, then the damage is already done to the chamber. Hopefully it won't be hurt at all though.

How many Loads do you have on those cases?

Do you use any "AMMONIA" containing Cleaners in your barrel, or any household cleaners containing it? If the anser is yes, that can cause embrittlement of the case and perhaps be the source of the problem.

If not, and depending on the number of reloads, you might want to just trash that Lot of cases.

I will test them out.

These cases were only fired twice. Once as factory ammo, then once in well below book max reloads. 30-06 winchester brass.

I use remington bore cleaner on a brush then wipe-out.

No dimples, extraction problems, other markings on the case.

I think it is a little corrosion, but I will see if they leak. I dip then cases in acetone and then bag them in ziplocs if I can't finish the relaoding at that time. Maybe a little moisture and bare metal.

Was wondering if theis is normal to pop up.

You dip them in acetone ?? Why ? Clean them in detergent and dry them . Slight discoloration is one thing , corrosion is another !

I dip them in acetone to remove the imperial sizing wax after sizing.

I sometime use it as a water displacement agent after ultrasonic cleaning also.