 .577/500 No 2 Black Powder Express

The .577/500 No 2 Black Powder Express, also known as the 12.7mm British No 2, is a British centerfire fire rifle cartridge.The .577/500 No 2 BPE was 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.