Thread: Strange marks on brass

OP said they have been de-capped and tumbled, not resized or FLS ie virtually fresh of the gun, once fired?? OP? Under normal circumstances those marks if from a die either with crud or excess lube would mostly blow out on firing. They are too sharp in relief to be formed by crud in a die. They are also
'bubbles" rather than dimples which are usually the symptom of excess lube. Of course the raised bits (bubbles) may be the areas without excess lube and the valleys where the lube did its mischief. But of course as always, I am probably wrong

Where my theory doesn't float is if it is corrosion why would it just be in the shoulder area.

Didn't think about them fired in a semi. Hope the previous owner of the brass doesn't still have a naughty gun.

In any case I would try for my money back on them.