In the late ‘80’s I came across some old .303 that melted the case head to the bolt of my rifle when fired.
Eleven years ago the gun shop for which I was working part-time required an inventory of their rare, tough-to-find, antique-ish ammunition.
We discovered a bunch of older (1920s vintage) ammunition for British sporting rifles - the sort used to hunt elephant, or lion or rhino, in Britain’s African and Indian colonial possessions back then.
Neck annealing was unknown then, and quite a number of the old rounds had developed cracks at their necks.
We pulled the bullets from a couple and found the charge retained by a card wad. Underneath the wads were strands of a reddish-brown material, up to two inches long. Looked very much like whole-wheat pasta, dried.
Placing a couple strands on a metal plate, we touched them off with a lighted match. They flared up and sizzled out in a very short time, just like smokeless powder will when unconfined.
Cordite.
The smoke & fumes smelled nothing like modern US smokeless powder, nor anything US smokeless powder from back in the day.