Interesting, the date has a defective bunter. Also, it’s a steel case.
I think this is a .50/.30 US XPL High Velocity.
ECRA Data Viewer 08 096 BGC 040
Yeah, but Lowell Mass didn’t do any .50/.30 work, so does seem suspicious. Balancing that suspicion is that it’s not easy swaging down a steel case like a brass case. Jess, does the case attract a magnet? (i.e. is it just a tinned brass case?)
It’s steel case