Hi Bob Wright,
When my family ( and me ) moved to the San Francisco Peninsula in 1964, a place I liked to play, was an 'undeveloped' little spot on the edge of suburbia, and, one day I found some old Copper Cartridge Shells in the gravelly dirt.
I did not save them, but, they were either .44 or .45, and Revolver length...and, I knew they were 'early' for being 'Copper'. They'd been mashed and were in poor shape and somewhat eroded and Pin Holey. But, someone had been shooting there I s'pose, way back when! And dumped their empty shells on the ground.
Was it only the Military Shells which were Copper in the beginning? Or, were the Commercials Shells Copper also for a while?
I think I recall that the Battle of Little Big Horn, the US Cavalry had 'Copper' Shells for their Revolver and Rifle Ammunition, and, that this had caused some troubles ( in the Rifles anyway ) when the Extractor would merely cut through that part of the Rim, and one had to hassle with the Cleaning Rod or a Pen Knife or other, to remove the now offending empty Shell from the Breech.
Also, if memory serve, the Alloy which was decided on to replace Copper, was then called "Bloomfield Guilding Metal"...which to the naïve Eye, would appear to be 'Brass'...but has a little more to it than Brass, as such, would tend to.
Are the Alloys used for present day 'Brass' Cartridge Cases, "Trade Secrets"? Or are they known?