Just a point of information: at the West Point Foundry Cove, in Cold
Spring, NY over 600 copper friction primers were found. I first saw
one of these in excavations at Fort McHenry. Basically a brass or
copper tube with primer in it with a ragged wire in it, when pulled,
the friction caused a spark igniting the primer. They were found
around the R.P. Parrot "gun platform" on top of wooden "grillage" in
the edge of the swamp, a set of "standard gauge" rails ran up to it
(almost a joke there were many "standards" at the outset of the Civil
War, one generally at the end of it, except for "narrow" gauge still
used in Alaska, Colorado, Mexico and perhaps elsewhere, a railroad
boxcar served pizza once in Skagway, Alaska, while the train was
hauling processed molybdenum ore from British Columbia, 1980, when the
vehicle road opened to Whitehorse, Yukon)

Two large "empty" shells were also recovered nearby the "gun platform"
(and iron pintle) which was found under the concrete stanchions (many)
of the large Chicago Steel and Bridge" shop remains, that had burned
down on the edge of Foundry Cove.