I don't know if this is the right place to post this but as most of the Apache crowd hang around here now I thought I'd share in here.
The other day I bought some inert rounds. I took a pic for size comparison and it's applicable here because I got a 30mm similar to what the M230 Chain Gun fires. Note that this is NOT an actual round that the U.S. Army typically fires through the gun, but it is compatible as is the 30mm DEFA round. Note further the brass casing as opposed to the light alloy of the M7xx ammo.
Left to right: Standard AA battery, .50 cal. Browning Machine Gun, 20mm Vulcan, 30mm ADEN.