Thanks for the information. I went to their site. They have listed .577/.450 cartridges for the Martini Henry (British Army) military rifle but not the .500/.450. I wonder if you meant the former rather than the latter.
Regards.
-------------------- "To the lover of art for its own sake it is frequently in its lowliest and least important manifestations that the keenest pleasure to be found." Sherlock Holmes in "The Adventure Of The Copper Beeches" by Sir Arthur Conan Doyle.