Actually... I have a few questions...
My concern (and question above...) was whether or not it was once-fired factory. If it is, that takes us a few places...
Was the primer crimped in and then removed? It's not got the NATO compass, but it's 5.56mm... so that suggests maybe it had a crimped in primer that may have been removed... and hosed the primer pocket in the process.
If the OP has reloaded that at least once, already, a 'too big' primer pocket suggests very high pressure, hence my concern.
The foreign primer pocket is a likely suspect... too bad there aren't any Tula or Wolf primers around, anymore.