From the collection ~ .577/500 No 2 BPE paper patched.
You'll notice in the top shot of the projectile there seems to be a copper plug in there possibly to aid expansion of the projectile?
What is the consensus on that theory!
Developed as a black powder round some time before 1879 by necking down the .577 Black Powder Express to .507-inches (12.9 mm) for use in single or double rifles, as well as a variety of Martini-based lever rifles.
MkVII 303 for scale