I have exemption on my 700HE belted cases.
You write a letter asking for exemption
for sporting use, include schematic or
a print of case and dimensions. Include
a list of sporting type guns it can be
used in. It takes a few months.All older NE and other
older over 50cal cases are grandfathered in.
Shotgun calibers are exempt as long as gun fires
shotgun cases.You can't take surplus 30mm and neck it
to 12ga and still be an exempt 12ga as it wouldn't
fire other 12ga cases.ED