Recently found some empty brass cases with headstamp “.410 x 73 MAG.“
and above that what appears to be"Gn3” with the 3 having an extended tail passing under the n.
The cases are 69 mm long with straight sides. They measure 11.90 mm in diameter at the neck and above the rim. The rim is 13.5 mm in diameter and 1.05 mm thick.
I can not find anything of this description in 'Cartridges Of The World” or on the internet.
Does anyone have any idea what these might be?