I have thousands of 9mm brass cases, scrounged from the local range.
I found one case with a belt on the inside. See the pictures.
The head does not indicate +P.
There is not another case stuck inside. The flash hole is clear.
I didn't reload it for fear of overpressuring.
Could it be an attempt to strengthen the base of the 9mm to avoid "the Glock Bulge" due to the unsupported area at the barrel loading ramp?
Any ideas?