Button or Shotgun Cap????

[stitchlips]

I found this where I have been finding a lot of civil war bullets. It was very deep. I thought it was a shotgun shell, but then I looked at the inside with a loupe. It appears to have fabric inside. Anyone know what this is?
Thanks in advance.

 

[Hookedondetecting]

I say old shot gun shell casing. Brass look half gone. They do make low brass shells. Upper part was cardboard and long gone
The inside is a dead giveaway! Reloded many of those in my day

 

[gsxraddict]

shotgun, it had a paper wad