I have tried to find the old trail as described by Eugene Ware in book Indian war of 1864. Early this fall I picked up four. After getting home a few days later, I could smell the aroma of burnt powder in my tote sack and dug them back out. The one was a dud but no lead.
Your finds appear to be fired Benet-Primed .45-70 cartridges (for the US Model-1873 Springfield "Government" Rifle) which were manufactured between March 1875 and March 1877 -- the month when the Frankford Arsenal first began marking the cartridge base with a headstamp. https://www.oldammo.com/november04.htm
Unless I'm missing something here (And normally I am) I'm seeing a dimple showing the firing pin struck it, the absence of the projectile shows it fire. So looks like a normal expended shell casing to me.
Honestly don't know how long the smell of powder remains in a shell casing, that is left in the elements.