Necked down some Alpha 6.5 Creed brass to 6mm last night. Left a nice little false shoulder for headspace, and they chambered like a champ.
One note: the Alpha brass had about 5% less capacity as Hornady 6 Creed brass… so I dropped a grain and half off the charge.
I hunt in some colder weather (sub 10 degrees) so only LRPs for me. Had some hangfire issues with SRPs in the cold with an x47.